Doroboneko! or something like that.
I'm not sure how this will play out. If the MC accepts the fourth heroine's request to go out, the other three have no chance of winning since the MC and Nanase would be together already. If the MC doesn't accept or is indecisive, this manga would devolve into just another harem romance with four girls. I don't see either of these options being particularly interesting, so hopefully the author comes up with something else.