I recently heard someone suggest Yumoto is aromantic
I'm not sure if this is canon, but I can tell you that it's heavily implied in the show, though I had never actually put my finger on it.
See, Yumoto never has one person in particular he feel close to in the club (unlike Atsushi and En or Io and Ryuu) but loves all of them equally. He never feels the need to pair off with someone (I know the others aren't confirmed to be in relationships, and I also ship At-chan and Kin-chan, but that's besides the point).
More specifically, I got this feeling from him in one of the earliest episodes, S1E3. The episode's villain tried to get everyone at school to love him, and succeeded with all of the other members of the club. When he tried with Yumoto, he was unaffected, and said he didn't understand it. It's not word-for-word confirmation, but this always stuck with me.
This is especially interesting because of the show's premise: fighting with the power of love. An aromantic protagonist seems like a contradiction, but in reality it's kind of perfect. It shows that 'love' doesn't have to refer to the romantic sense, as is hinted towards through Ryuu. Yumoto does love his friends, but he doesn't feel romantic attraction, and that love is just as true and just as powerful-- possibly more so, since he's the only one able to land finishing moves.
Whether or not this is ever officially confirmed, it works really well, and is a perfect way to approach Yumoto's character.
