it's definitely one of those situations where tachi is trying to test the waters to see if neko "likes" him and then when neko starts to talk to that one girl trying "new" things tachi gonna get jealous and shit goes down idk just my speculations
ugh get the fuck off the screen fucker and to param it's totally fine to also be sexually/physically attracted to your partner. as long as you know you also love them having desire for them is totally part of the norm unless you're asexual!!
IM CRYING THIS IS SO HEARTWARMING BUT NOW I REDHEAD BETTER GET HIS HAPPY ENDING TOO