Mimi has some of the friendliest and most relaxed rabbits we've encountered in Tokyo - we were impressed with how well they get along with each other, and how easy-going they are with human visitors. Unlike other cafes that allow only one or two rabbits out of their cages at one time, the playroom at Mimi is a non-stop rabbit party, with rabbits chasing each other around and snuggling up to visitors.
Since our last visit, Mimi has added a new room devoted to otters, and if anything, the otters are even more outgoing and social than the rabbits. The dozen or so otters seem to enjoy meeting people and cuddling in their laps, as well as playing with their toys and socializing with their otter friends. They also seem to like napping quite a bit, so don't be surprised to find a sleepy otter dozing off in your lap while you pet it.
Advance reservations are recommended even on weekdays, although there may be space for walk-ins if you're prepared to wait. Check the website for reservation guidance. The one-hour cover charge here includes one drink (coffee or tea), which will be served to you at the end of your visit. As usual, try to visit on a weekday if you can, to avoid the crowds.