Oichi is one of Nobunaga's younger sisters and Nagamasa's wife. Historically, she later becomes Katsuie's wife, which is implied to also occur in select Koei titles. Cherished by her family and said to have been well loved by their retainers for her beauty, Oichi is the famous mother of the Three Azai Sisters.
Oichi is a kind individual who believes in her loved ones. After helping her brother at Okehazama, she joins the Oda ranks at Inabayama Castle. Though worried for her sister-in-law's feelings, the elder calms her by merely stating that she is making a choice. Contemplating Noh's words, she marries to Nagamasa and is forced to fight her brother years later at Anegawa. Wanting to find an alternative solution to the conflict, she believes that Noh can convince Nobunaga to stop while defending her husband and Yoshikage.
If she fails to succeed in either task, she gives into fighting her brother and believes that she is the only one capable of killing him. Despite Oda officers and her husband trying to dissuade her from this path, she aids the Azai march at Azuchi Castle to take Nobunaga's life. They succeed and Nagamasa becomes the near unifier of the land. Noh, mad with Nobunaga's death, leads the remaining Oda officers into rebellion at Honnōji. As they fight, Ieyasu and Hideyoshi also voice their objection to Nagamasa's new seat of power. Slaying a majority of the Oda followers, Oichi is resolute to continue fighting beside her love in her brother's name.
An Oichi who quickly routs Nobunaga at Anegawa saves the Azai main camp from danger. Hoping to fulfill her wish, she hurries to meet her brother in Azuchi Castle to negotiate peace between her two families. Arriving at the top floor, she instead meets Mitsuhide and learns of his plans to defect. With this in mind, she and her husband hurry to Nobunaga's rescue at Honnōji. She convinces her brother to live past the betrayal and he escapes with Noh and Ranmaru. Enjoying a fireworks show after their victory, the two men share a brief exchange of apologies and reconcile.
In Samurai Warriors 2, she begins her story happily married with Nagamasa yet distrusts her brother's word of good faith for his alliance with the Azai. Grabbing the closest weapon she could find, she joins her husband in suppressing bandits in a nearby village. As Nobunaga breaks his promise to not attack the Asakura, Nagamasa decides to pursue the Oda to aid his family allies. Oichi, wanting to fight for her lover than her family, joins the chase at Kanegasaki and aids the Azai-Asakura front at Anegawa.
Winning the latter conflict causes the formerly conquered forces to revolt against Nobunaga. Taking advantage of this time of weakness, Yoshikage declares himself leader of the resistance and asks both Nagamasa and Oichi to attend the fight at Mt. Usa. Although they are successful, Nobunaga regroups, deals with the rebels, and surrounds Nagamasa and Yoshikage at Odani Castle. Incredibly guilt-ridden for his actions and knowing that he wouldn't survive, Nagamasa sends Oichi back to the Oda. Nobunaga then orders his sister to lead the attack and end the Azai-Asakura alliance permanently. As per her husband's wish, she strikes him down in combat. Crying over his body, she sadly confesses her love for him a final time before he disappears into several flower petals.
Her dream stage is a contest staged by Nō at Shizugatake. Wanting to find a definitive answer over which one is the most beautiful, they clash with the Oda supporting Nō and the Azai supporting Oichi. Although she initially states that the battle is pointless, Oichi humorously gives in to the competition to prove that she is at least more beautiful than her sister-in-law.
In Samurai Warriors: Katana, Oichi first appears in the Ascendancy scenario blocking her brother's escape from Kanegasaki. She becomes the player's opponent if they manage to reach Nobunaga in time. Her resistance against Hideyoshi is revisited in the Savior scenario. After Katsuie's defeat, the maiden leaves the battlefield to seek refuge in her husband's castle keep. There, she commends the protagonist for quelling the chaos before choosing to fight him for his assault on her clan's troops. Their fight is stopped by Nene who convinces Oichi to leave the Oda in Hideyoshi's care while residing with the Saika for her own safety.
Her stay in the village is relatively peaceful until Nō argues with her and the other women over who is more beautiful. Their quarrel escalates until Magoichi suggests a beauty contest to settle the issue. Oichi consents to the player's role as judge when he frees her from Kanbei Kuroda who had been ordered by Hideyoshi to instigate her kidnapping. During the competition, she may be chosen as the victor or feel insulted if the protagonist prefers brashness over elegance.
Again joining her brother's ranks at Okehazama in the third title, she has a chance meeting with Nagamasa while paying her respects to a fallen soldier. Joyfully curious about the cheerful stranger, she decides to enter the fray to learn more about him. As the Oda officers notice the love between them, both lovers marry due to their feelings for one another and have their blessings from the Oda family. Though becoming good friends with his brother-in-law, Nobunaga tells his sister that she is the only one capable of making her wishes come true. Her dream is to help support Nagamasa's vision of a serene land filled with flowers, which she affirms after helping her brother take Inabayama Castle. When Nagamasa decides to aid Yoshikage, Oichi realizes that her husband's kindness causes her anxiety and hesitates to fight her brother. Both Nobunaga and Nagamasa notice her strain, suggesting that she return to her brother if her husband's decision pains her too much. Touched by her husband's sincerity, Oichi decides to stay by the Azai through any hardship and swears to strike down Nobunaga.
In spite of her newfound devotion, Nagamasa asks her to leave for the Oda after the Asakura fall and wait for the country he wants to create. On her trip back, she realizes her husband's dream can be made a reality with her beside him and rides back alone to rescue Nagamasa at Odani Castle. Telling her husband that they can realize his vision together, the lovers reunite and protect the castle. Routing her brother's army, they eventually gain the potential to see their dream realized. However, Shingen, Ujiyasu, Kenshin, Motonari, Ieyasu, and Nobunaga oppose their rise to power and lead their armies against them at the Yogoko Lakeside. Striving to prove their love and conviction to the other lords, Nagamasa declares the conflict will be their last battle. Upon their victory and the other lords' consent, Oichi and her husband share a happy moment in the gentle, new peace.
In Sengoku Musou 3: Empires, Oichi warns her brother of the Azai's betrayal by sending him a bag of beans in his story route. However, this results in Nagamasa's demise and her return to the Oda. Overcome by sorrow, she is consoled by Toshiie when he offers to cheer her up with his wife's homemade onigiri. Hideyoshi's story has her survive Shizugatake and be taken in by the Hashiba clan. While isolating herself and possibly contemplating suicide, the maiden receives a visit from Nene who complains about her husband sending the former so many letters while secretly removing the blade placed in front of her. Touched by Nene's concern, she resolves to move on from her suffering and live.
Samurai Warriors 4 Oichi decides to protect her brother's future at Okehazama. She is married to Nagamasa soon afterwards, happily being with him when he is loyal to the Oda and enjoying the fight for his dream after his betrayal. Several days after Anegawa, however, Oichi secretly confers with Yoshitsugu to ask if they have a chance of succeeding. The strategist bluntly tells her their cause is lost. Accepting the truth he gives her, Oichi keeps it to herself in her desire to live out the last of Nagamasa's passion by his side.
Regardless of whatever end her husband faces, Oichi survives and braves her grief to again join the Oda forces. Her motivations for doing so is to avenge Nagamasa by punishing the real culprit behind his demise. She may threaten him at Nagashino and gain a chance to personally end her grudge at Kii Province. Katsuie senses she likely has a death wish with her self-imposed mission, and she is genuinely touched by his sincerity to be her eternal guardian.
The Oda fall into decline years later due to Hideyoshi's rising influence. Oichi is caught within the political crossfire for Nobunaga's successor by being politically married to Katsuie. Seeking to repay her newfound affections for the general, Oichi prefers to face annihilation with him at Shizugatake. She hopes her dreams of peace will live on in the hearts of the victors as she follows Katsuie into the burning Kitanosho Castle. Moments after she conveys her feelings for him, the narration states the couple perish together in the flames.
In the Samurai Warriors 4-II Loyalty Story, she adopts a maternal role for Takatora. Oichi worries for him at Nagashino and seeks a good future for him. She denounces his sentiments for her at Shizugatake, insisting that he treasure his values and respect hers. She ends her life off-screen within the burning Kitanosho Castle. The Blossom Shower Story has Gracia and company barge into Oichi and Katsuie's quarters and fight for the married couple's survival at Shizugatake. Gracia places both of them under a spell for their compliance which leads them to join the idol group's stage performances.
The husband and wives downloadable scenario has Oichi support Nagamasa for the competition.
Spirit of the Sanada only gives Oichi the supporting role of being Nagamasa's wife and Chacha's mother, helping her husband resist her brother with other anti-Nobunaga forces. When Nagamasa is cornered at Ōdani, Oichi and Chacha are sent out to not suffer the same fate. She is killed with Katsuie at Shizugatake shortly after.
Her struggle along with Nagamasa's perplexes the young Chacha, who wonders why they would still fight and resist against hopeless odds.
Throughout the series, Oichi is faithfully following Nagamasa. During Warriors Orochi, she joins his resistance against Cao Pi and is given the task to guard their allies' reinforcement point. Following their defeat, she wishes to share the same fate as her lord and joins Wei's ranks.
In Warriors Orochi 2, she acts as Yoshikage Asakura's guide to Nagamasa. She states that her husband's noble character allowed her to gain their ally. She shares her dream mode with Sun Shang Xiang and Da Qiao. In this stage, she works with her teammates to protect a petrified Nagamasa, who was frozen by Da Ji. After defeating Okuni and a lecherous Dong Zhuo, the spell over her lover is broken and he is free to move once more.
After Orochi's second defeat, she joined her husband's dream to create a land of harmony. They were overwhelmed by the serpent forces, however, and she is taken hostage for Nagamasa's loyalty. She and the other prisoners are rescued by the coalition at Xuchang. When freed the maiden once again swears to be beside her husband's side. She later supports their efforts to rescue Diaochanand Wang Yi in the past.
During Ultimate, Oichi is charged with the defense of the Oda main camp at Nanjun during their confrontation with the Wei army. When her brother and his retainers disappear, Oichi returns to join the Azai, but finds that Nagamasa has changed considerably. Seeing no alternative, she joins the Wei army at Tedorigawa in order to reach Nagamasa, who has encouraged Ma Chao to attack Cao Cao. Shortly after the battle, the Nagamasa beside the young general is revealed to be a clone of the real one.
Accompanying her husband and Takatora to the new world, they are immediately surrounded by Da Ji's army at Nanzhong and are fighting for their lives. Thanks to the arrival of Yukimura and the Coalition army, they are able to attain victory, but the accompanying Perseus would be kidnapped by Zhong Hui. Grateful for the rescue, Oichi and the rest of the Azai army volunteer to help the Coalition search for the demi-god.
She later assists Xun Yu and Cao Cao in investigating the whereabouts of two new heroes that have appeared at Komaki-Nagakute-Xiaopei
Her counterpart in Pokémon Conquest is not noted to be married to any particular person. She once enjoyed Nobunaga's company since he was kind and gentle, but once his behavior soured, she distanced herself from him. Oichi misinterprets her brother's ambition and fears he wants to destroy all of Ransei. To escape the war he commits to waging, Oichi runs away from her home, Dragnor, with her beloved Pokémon partner Jigglypuff.
When the main story begins, she happens to arrive at Aurora Castle. She spies the protagonist, who is the newly made Warlord of the country, being intimidated by two generals of the nearby kingdom of Ignis. Unable to turn away from the fight, Oichi supports him/her and helps defend Aurora. She then pleads for the protagonist to let her stay and rejoices living in a land of peace. She quickly becomes fond of her new friend and home, offering advice for the player during the tutorial stages of the game. Though she is reluctant to participate, Oichi is also a mandatory character in the decisive battles throughout the main story. The protagonist is often mute during story events, so she acts as his/her in-game interpreter for his/her feelings.
As she stays with the protagonist, Oichi eventually reveals her origins to him/her and her wish to see Ransei unified with peaceful intentions. She implores him/her to create such a land with her support. For this wish, she remains loyal to Aurora as they face Nobunaga's allies and forces. After the legendary Pokémon decides to depart from Ransei, Oichi congratulates the protagonist's successful unification. Despite her reconciliation with her brother, she accompanies the protagonist back to Aurora.
Oichi's episode has her act as Pugilis's Warlord as one of the beauties in Ransei. The six other female Warlords fight amongst themselves to decide who deserves to be known as the Queen of Ransei. Oichi personally has no interest in the competition, but she is goaded by Nō to fight for her believers. In other episodes, she often serves as a substitute Warlord for either the protagonist or her brother in their absence.
And she is reprised by Tara Platt in the English dub and Ai Maeda in the Japanese dub.