Tsundere is a Japanese term used to describe a character development process that depicts a character with an initially harsh personality who gradually reveals a warmer, friendlier side over time. The word is derived from the terms "tsun tsun" and "dere dere". The term is typically used to describe anime characters who act rude, cold, and hostile towards their love interest in order to conceal their warm and caring feelings. A tsundere character may be harbouring a secret crush, or a pivotal moment could leave them suddenly infatuated. The concept has received increasing attention in Japan, with tsundere-themed products released and the concept increasingly reflected in recent anime.

Tsundere is an adjective used to describe a person or character who swings between emotionally hot and cold, in particular when dealing with a love interest. The term is typically used to describe female characters, especially tomboys who occasionally show some girly tendencies. The term has become more and more about characters that switch between cranky and affectionate in an instant, versus a slow burn change driven by the plot.

In summary, tsundere is a term used to describe a character development process in anime where a character initially has a harsh personality but gradually reveals a warmer, friendlier side over time. The term is typically used to describe female characters who act rude, cold, and hostile towards their love interest in order to conceal their warm and caring feelings.