Audience Surrogate: Just like the readers, he needs to be introduced to the whole ideas of biology, reproduction and society of the Madararui. He even lampshades somethings like the huge Artistic License the plot takes on Biology and the screwed up family tree of the Madarame.
Even the Guys Want Him: Mostly played for laughs in the start, but later on, it becomes clear he is actually very attractive to men and it drives Kunimasa insane.
If It's You, It's Okay: He is only attracted to Kunimasa, as far as males goes, to the point of turning down Hidekuni, who is a much kinder alternative and very similar to Kunimasa. He even points out he was originally straight.
Living Emotional Crutch: Becomes this to Kunimasa, as it gets clear that without him, Kunimasa slowly reverts back to the cold and distant persona he had before meeting him.
Mr. Seahorse: Kunimasa wants him to bear his children, though he starting to grasp the concept, it still scares him.
Took a Level in Badass: During the summer trip, he becomes more capable of controlling his powers and even stands up to Makio and Nanami.
Wholesome Crossdresser: Due to Yonekuni can't standing being near men. After a while, this is subverted and Yonekuni can stand being near him while he is dressed normally.
Uke: A deconstructed version, he is much more assertive and less submissive than what would normally be expected of an uke.
Voiced by: Yoshihisa Kawahara (OVA), Kiyoyuki Yanada (Drama CD)
Badass in Distress: While it's clear he is freakishly strong, he is subdued and kidnapped by Makio.
Character Development: Gets kinder and more open about his feelings for Norio, going from simply wanting him to have his kids to genuinely wanting to start a family with him.
Crazy Jealous Guy: He has an almost murderous strike to anyone who shows interest in Norio, which includes Teruhiko, Mc Bear(who wasn't actually interested) and Hidekuni(his brother).
Heroic Sacrifice: When he was a kid, he offered himself to go with Makio so his brother wouldn't have to, this made him a pretty messed up person.
Master of the Mixed Message: Norio spends a long time wondering what exactly are Kunimasa's feelings for him, due to Kunimasa refusing to actually act like a couple or as if he has feelings for him, while at the same time keeping him away from every other male and wanting to make out with him at every opportunity. He drops this later on and genuinely starts to care for Norio as a possible life partner, rather than a baby making machine.
Seme: Deconstructed, though he seems like an average seme, he is much more emotionally damaged and fragile than he lets on, to the point of having Tsundere tendencies.
Smells Sexy: His smell is the main thing that started Norio interest on him.
Tsundere: Reveals that he does not like to talk about his feelings and that he was lying when he said he only wanted Norio to have his kids. After this, he becomes legitimately nice to him, even proposing to him.
"Not If They Enjoyed It" Rationalization: He believes to have raped Shiro while he was out of it, but after realizing that Shiro enjoyed it, he states that it was sex, though he was very mad with both Shiro and Kunimasa at the time, so he might not really meant it.
Odd Friendship: He really becomes closer to Norio, and even acts as his confidant when he needs to talk about Kunimasa. It helps that he does support their relationship.