Len raging off!!If it felt that good, why don't you marry those geezers so you can have sex every day?Len-kun!*rush*Big sis Miku, you bitch!
The word "bitch" is a piece of borrowed English slang in Japan, albeit with a tweaked meaning. There, it has greater connotations of "slut" (and very little of "mean girl") which Len is using it as.*flustered*