A lot of romance stories mistake “drama” for “depth,” so the stable caring character gets sidelined because they don’t create constant conflict. But many Kashima fans actually find him more compelling because he acts mature while still hurting underneath.
So if the manga ends with him once again stepping aside “for Toono’s happiness,” a huge part of the fandom is probably going to feel devastated rather than satisfied and I am definitely one of them.

Kashima isn’t even boring. He’s one of the most emotionally layered characters in the manga:
-he hides insecurity under composure
-he’s possessive but restrains himself
-he notices Toono deeply
and he tries to love without controlling.
That’s why many of us get protective of him. He feels painfully realistic compared to the more chaotic chemistry-driven dynamics.