The female characters frequently act in an endearingly childlike fashion, which is described by the Japanese slang term "moe", a characteristic that is often looked-for in "bishōjo" characters. The reasons for this characteristic are not always merely sexual: sometimes it is used to present a pretty and affectionate character who is beloved and supported by the player. In fact, "little sisters" are a recurring fixture of "bishōjo" games. A very popular game that emphasizes the characteristic of "moe" is "Sister Princess", based on the premise of the player acquiring no fewer than twelve little sisters.