It seems that Ibusuki cannot see Eve but can see others because the first love was half-fulfilled with Tarou confessing. It's interesting because I like the Eve and Ibusuki combo and like them spending time together.
So far, the formula seems to go:
Confessed to by first love + reject first love + get hit in the head = stop seeing first love zombies altogether
Confessed to by first love + reject first love + headbutt[get hit in the head] = lose ability and pass it to someone else
Get hit in the head (again) and faint = reset/return of ability
@herasmus I agree. I think we may get a plot twist that first love zombies don't disappear when there is mutual confession but fused with the girl as the realization of first love makes them real and not fantasy anymore. Kinda like instead of disappearing to snow globe, they go back to where they really belong