Tsundere (ツンデレ, pronounced[t͡sɯndeɾe]) is a Japanese term for 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 (ツンツン) (adverb, 'morosely, aloofly, offputtingly')[1][2][3] and dere dere (でれでれ) (adverb, 'in a lovey-dovey or infatuated manner').[4][2][5] Originally found in Japanese bishōjo games,[6] the word is now part of the otaku moe phenomenon,[7] reaching into other media. The term was made popular in the visual novel Kimi ga Nozomu Eien.[8]