Here are some resources for finding Yesung’s cafe called 마우스래빗 or Mouse Rabbit! I’ve never been there, so I can’t give my own directions, but I’ll provide links to other people’s sites!
Address:
5-14 Hwayang-dong, Gwangjin-gu, Seoul, South Korea (서울 광진구 화양동 5-14번지)
1-Directions and pictures (<<This girl actually met Yesung when she was there!!! Whaaaat!?)
3-Video of Directions
4-Directions and pictures
pictures gotten from directions sources 1 and 4
Kpop Tour Guide 