Yeah if anything, Kumugi pairs well with Ichi in that sense (the romcom sense mostly) but in terms of a nice sibling-like relationship, Ichi and Dascaras are excellent as a duo. It's obvious Ichi is a caring person, and he could probably tell she was feeling off, he's oddly perceptive. And Dascaras is fairly caring too, even with her diva-ness.
Honestly, I like pretty much all of the characters in this manga, they all are interesting and fulfill their relative niches really well.

Im not ship them as romance but that lap scene is so badass and beautiful.. like just being them silent comfort!! I love it!!