Adult chocci elf coming from the future and planting a kiss on MC was not really that weird to me, since she was always in love with him and that love grew when he died.
But man, protagonist-kun marrying her it’s just freaking weird. He was saying all the time how wrong it is, and always stated how he didn’t want to be that type of pervert, but ended up being one. He wanted to reciprocate future Yuel’s feelings but that doesn’t make any sense, since current Yuel is not adult Yuel. Adult chocci elf disappeared because her timeline was no more.