MC was a bit shy and at that time he was going to ask the girl out or confess (I don’t remember exactly) but because he hesitated she left (she was a true tsundere). Then a girl appeared in front of MC, he realized it was her many years later. She said she was married and grinned, showing him her wedding ring. When MC was disappointed she said the person she married was him. Then she taught MC how to confess to her in the present time. She had sex with him and gave him tips, after MC confessed to the girl in the present time, suddenly the girl from the future accidentally came out of the closet. Then MC had to explain everything. I was impressed by the smile of the girl when she showed off her wedding ring. I would appreciate it if anyone could help me find it.