Manga by author Yukimori Nene

Shiraishi is a plain boy who is two hairs short from being invisible to his classmates and peers; in other words a "mob" character. Cue Kubo, his beautiful next-seat neighbor who always notices him and playfully experiments on him to gauge just how "invisible" he really is... and then she declares herself his "heroine".

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The boy I met that day is a grandpa now, and I can't be a grandma with him because I'm a demon. Why are you a human and I'm a demon?A slightly painful tale of a boy carrying darkness and a demon who doesn't know love.