Rin Obami is a member of The Hundred Devouring Families. He arrived to the Hyakkaou Private Academy to gamble against Kirari Momobami in order to dethrone her from student council president position and thus choosing a new leader of their clan. His branch is widely known for being good swindlers.
Rin's short black hair (dark blue in the anime) is styled with a straight cut fringe framed by longer side bangs that hang just below chin length area. Atop the neat hairstyle is a little curl on the right side of his head. His eyes are relatively large that are mildly black (dark violet in the anime). He wears a standard male Hyakkaou Private Academy issued uniform.
Rin bears a polite demeanor, often speaking calmly. Given he's a swindler, however, this is nothing more than a façade used to gain others' trust while simultaneously looking down on them. He's noticed to be very handsome by many girls in the school, which he uses to his own ends, mostly to win matches. When he gets real, he has an evil look and speaks his mind, able to startle even Kirari Momobami. He is very intelligent and will mentally back his enemies into a corner by exposing them, simply to win. Rin mentions that he likes to investigate his enemies and know them better in order to beat them. He has got a very gleeful side.
The relationship with Ibara Obami seems good, but Rin is actually just using him for his own scheme. By far Rin's most notorious traits are his inflated ego and his great ambitions. He believes himself to be the better person to lead the Momobami clan and thus does anything he can to trounce Kirari from her seat. Deep down, however, he has a severe inferiority complex towards Kirari as a result of a match between the two in their childhood in which Kirari officially lost, but in fact won due to Rin's cheating.
It is implied by Ibara that as a result of this deep blow to his ego, Rin has made it a habit to look down on others in order to keep his own fragile ego afloat, and tries to beat the Momobami twins to restore his confidence. After Ibara defends him, he reveals that he did care for Ibara all along and simply lied to him in an attempt to protect Ibara from the family. Rin also tried to lie to himself about his caring feelings, since he didn't want them to get in the way of his ambitions. This is most notably seen where he was shown to be secretly hurt when he asked Ibara if he thought he was "dirty" upon the latter catching on to him manipulating him for his own benefit and being confronted about it.
Later after losing to Ririka and overcoming his feelings of inferiority towards Kirari and Ririka and being comforted by Ibara, Rin was shown to show more positive traits of his personality more openly. This is seen where he was shown to now openly express his pride and care for his brother's personal growth openly to Terano.
At some point when they were still kids, Rin played a game against Kirari Momobami in front of the whole family. He had a great cheat, but she still saw through it. But he still won, because she purposefully didn't reveal it. For a swindler, even if the plan works, nothing is worse than being found out. This feeling of defeat deeply crushed him and he needed to take revenge on Kirari. So everything he did was to eventually reach that goal. He also learned to not show his emotions. When he found out Ibara wasn't able to tell lies, he took him under his wing and allowing him to stay in the family. But Rin only uses Ibara for his own plans, which is an acceptable arrangement for Ibara since he sees Rin as his protector.
For the election of a new president at the academy, he came to fight over the seat. He usually spends time in his room drinking tea. One time, he was talking with Ibara about the relationship between Miri Yobami and Miyo Inbami. He then asked Rei Batsubami on who she thinks will win the ongoing game, but she states she has no idea. Rin smiles and remarks how she never changes.
Together with Sumika Warakubami, he challenged Kirari to a card game, after she said she was bored. He was eager to beat her at first, but soon realized, that she scared off most of her opponents simply by betting everything. He pointed out, how cheap he found this tactic and wanted to play for real. Kirari's excitement was abruptly stopped after he simply left, not wanting to play such an dishonorable game.
He found her surprised look very amusing and laughs about it. He then remarks, that he knows enough about her and wants to find out more about Ririka Momobami.
He is also present at the second broadcast, since he gained a bunch of votes. He is intrigued by Yumeko Jabami's gambling invitation. He is also at the vote auction. There he gave the bet-pad to his Rin, which led to them being found out. Rin also can't believe it, when Rei reveals herself. However he does realize, that it was their own mistake for underestimating her so much. When Ibara gets angry at Yumeko for betting so much, he holds him down, since he deduces that Yumeko is probably trying to figure something out by betting so much.
Later, he invents Scumcoins in order to get votes from other people. Per vote Ibara gives out one Scumcoin. He gained a lot of votes and was certain to beat Kirari. Most of the students cheered him on and the girls also found him attractive. He sends Nozomi Komabami to challenge Ririka and hopefully beat her. But that didn't work and Ririka now wants to gamble against Rin. Rin is worried at first but then decides to give her a taste of what it's really like to be devoured. He then contacts someone to pose as a fake election observer and organizes an entire fake game, called War!.
He asks Anzu, Aruka and Midori to play as well. He wants them since they aren't good gamblers and he doesn't want a hard time. His plan was to just collect the votes if he wins or reveal his scheme if he loses. During the game he is able to hold himself quite well and also use Ibara to his benefit. Near the end of the game, Ririka reveals his lies about the three girls and thus everyone acts against him and he loses. Because of that, he reveals Kurara Kurokura as an impostor and quits the game. He explains to the others that the election doesn't have a real purpose except entertain Kirari. He states he must beat her, not only because of his childhood but also so that she gets pushed off her throne.
Ibara is angry at Rin for lying to everyone and even him, in which Ririka Momobami declares them both liars. Since the truth that they don't want to accept, it is actually revealed that they care about each other. Then, Runa Yomozuki storms in and declares the game as valid, which shocks Rin and he is out of the election. The others make fun of him and his life as a swindler is basically over. But Ibara stands up for Rin and doesn't let the others mock and insult him. They tell him he is dirty liar whose life is worth nothing. He tells Ibara that he only ever lied to him in order to protect him and make him feel better. He then apologizes to the others and leaves with Rin, smiling.
His trick with the fake observer has left some impact on the election, much to Runa's annoyance. So the security on the tournament is higher now. Rin watches Ibara on the phone. He hopes that he doesn't push himself, especially since Miyo's poison is just as deadly on family members. He is impressed that Ibara manages to use his honest reputation for his benefit. But he is sad, that Miyo had to be his opponent. Ibara loses, but gains some confidence nonetheless. Rin then talks to Terano about how happy he is, that Ibara learnt something with those last few votes. He does dislike having to go home though. He also notes how the defeated should always butter up the winners.
- Gambling Girls again (non-speaking)
- The Girls of the Momobami Clan
- Communicating Girls
- The Girl Who Changes
- The Girl by her Side (non-speaking)
- The Logical Girl
- The Girl who Bears the X
- The Null Girl
- The name Rin means "cold, strict, severe" (凛) (rin).
- Rin's surname, Obami, means "tail, end, counter for fish, lower slope of mountain" (尾) (o) and "bite" (喰) (bami).
- During flashback in chapter 57, Rin presents himself to Ibara as the main member of Obami family during flashback and Nozomi Momobami reveals that Ibara is a member of Obami's branch family.