Sorry for the confusing descriptions

The first is about a high school girl whose father is a chemist. Her younger neighbor whom she has a crush on is a genius and borrows her dad's books. Apparently they are married in the future. One day his future self appears, and his younger self gets jealous because he likes the girl. One thing I remember is that both his younger and future self lick the rim of the coffee cup after taking a sip.

The second manga is one I read once but have never been able to find again, so I hope someone knows it. I don't remember many specifics, but it's about a high school girl who is dating an older, working man. The girl wants to have sex with the man, but he wants to wait until she is of legal age. Eventually she wears him down and they have sex, but their relationship is discovered and the man is arrested. When he is released he asks for the evidence they took from his apartment because in it is an engagement ring that he had planned on giving the girl. He proposes to her and everything works out.

Can anyone help me find these?? I believe the first one was the last chapter of either a series of oneshots or the last chapter (an extra) of a few-chapters story (I think it is chapter 5 or 6). I have no clue about the second one.

The first one is Ghost wa Kiss o Kirau, the story Mirai kara Kuta Danna-sama.

I'm in idol hell T.T

Yes, this is it! Thank you!!