Motoko Aoyama comes from a famous line of swordsmen from Kyoto. Her family are the proprietors of the God's Cry School. Growing up, Motoko was always in awe of her older sister, Tsuruko. One day, Motoko caught her sister and her fiancee in the intimate act of kissing. This had a profound affect on her; causing her hatred and fear of both turtles and men. Shortly after this, Motoko left Kyoto to stay at the Hinata House girls dorm. She was the last resident to arrive before Keitaro came.
At Hinata House
Motoko is perhaps the one character who undergoes the most growth during Love Hina(even more so than Keitaro). When the series begins, she is very formal and dedicated to her swordcraft. She has a hatred of men, especially men she considers to be perverted or weak(like Keitaro). The first hint that there may be more to her than there appears, comes at the end of the first volume. She begins feeling weak and feverish, and is afraid that she's falling in love with Keitaro. It turns out that she is just suffering from a cold.
As much as Motoko insults Keitaro for being unmasculine; she herself is insecure about her femininity. She once challenged Keitaro to a duel, and when he somehow won his prize for winning was to ask Motoko to act more like a woman and less like a warrior. The other residents helped her out by giving her a makeover and putting her in a miniskirt. Motoko even tries her hand at stereotypical chores like cooking and cleaning. Unfortunately, this makes her feel helpless and miserable. Keitaro apologizes for hurting her feelings, and she challenges him to a rematch which she wins easily. She refuses to punish him though, and says that if there is a woman who is unfeminine, then she must be balanced by a man who is unmasculine.
When the gang goes traveling, Motoko is usually paired with Kitsune. She and Kitsune are somewhat of an "odd couple"; the free spirit lustful gambler, and the stoic and formal swordswoman. They first go traveling to search for Shinobu and Su who themselves have gone in search of Keitaro and Naru. Motoko soon discovers that Kitsune's real motive appears to be eating lots of local delicacies. They run out of money, and Motoko is forced to perform swordtricks for passerby to earn yen. They finally catch up with Shinobu and Su, and manage to rescue them from some yakuza. They eventually track Keitaro and Naru down, and they all head back to Hinata House.
Much the same thing happens when they travel to the island of Parakelse. Motoko and Kitsune, this time joined by Mutsumi have come to the island searching for Puffy Mushroom(Shinobu, Su, and Sarah) who were lost looking for Keitaro and Naru. This time, Kitsune dresses Motoko in a leaf bikini in order to hitch a ride, but ends up causing a major traffic accident.
Motoko is the only one at Hinata House who has the stamina to keep up with Kaolla Su. Su seems to have somewhat romantic intentions on Motoko, though with Su's personality it can be hard to tell when she's playing and when she is serious. Once, Shinobu was interested in learning about kissing so Su created a special kiss training companion named Krishna-chan. Krishna-chan ran amok, and wound up running into poor Motoko and kissing her. Motoko is horrified, and Su deduces that the machine must have been her first kiss. To make it up to her, Su gives her another kiss and then gushes that Motoko was her first. She then embarrasses Motoko further by saying that she tasted like soy sauce. Later, when Su kidnaps Keitaro on the island of Molmol she tells him that she wants to take Motoko as a lover/bodyguard.
Motoko's complicated relationship with her sister is first explored in vol.9 when Tsuruko comes to Hinata House and tells Motoko that it's time for her to take over the family's dojo. Motoko doesn't want to, so she fakes an engagement to Keitaro(according to family tradition if a daughter wed she was not able to take over the school). Tsuruko later discovers the truth, and she defeats Motoko in a duel. She forces Motoko to live as a normal high school student until she able to defeat her. If after three days, she still can't defeat her, Tsuruko will actually force her to marry Keitaro. Tsuruko secretly tells Keitaro that she wants him to help Motoko defeat her. She tells him about Motoko walking in on her and her husband, and that defeating her will be the only way Motoko will become whole. With Keitaro's help, Motoko finally defeats her sister. Tsuruko is secretly pleased.
As much hell as Motoko put Keitaro through for being a ronin, the tables are turned when she also fails the Tokyo University entrance exam. To make matters worse, she pulls a Keitaro and tels her family that she made it in. Tsuruko comes to Hinata House to congratulate her, and when the truth comes out that she failed and has spent her spare time writing tawdry romance stories, she fights Motoko and calls her pathetic. Motoko realizes that her sister is right, and announces her intention to leave Hinata House and become a nun.
She cuts her hair and leaves Hinata House. Keitaro follows her and convinces her to let him help her study. He gives her an old mechanical pencil of his for luck. Keitaro ends up dozing off while they study, and Motoko reminisces about her past dealings with Tsuruko and Keitaro. She comes to the conclusion that she thinks too much, and then pretends everything's okay by hiding her weaknesses. Tsuruko gets the jump on her with a surprise attack, but Motoko manages to win by blocking the Tsuruko's sword with the lucky pencil. Motoko refuses to deny her feelings any longer, and announces her love for Keitaro. Satisfied, Tsuruko leaves her be.
By Love Hina's epilogue, Motoko has become a third year law student at Tokyo U, proprietor of the God's Cry School in Kyoto, and also a successful part-time romance novelist.