Yukiko Horiguchi (堀口 悠紀子, Horiguchi Yukiko, born 28 January 1983) is a Japanese animator and illustrator from Kyoto Prefecture who worked for the anime studio Kyoto Animation. When illustrating a light novel, she uses the pen name "Shiromizakana" (白身魚). She is best known as the character designer for the anime adaptations of K-On! and Lucky Star and as the illustrator of the light novel series Kokoro Connect.^[1]

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She is the older sister of BUNBUN (also known as abec), the original character designer for the anime Sakura Quest and the illustrator of the light novel series Sword Art Online and Sword Art Online: Progressive. She is close to her brother and was once part of a doujinshi circle with him.

After graduating from junior college, Horiguchi joined Kyoto Animation in 2003. Her first position was as an animator for the television anime Crayon Shin-chan, and began work as a key animator for the first time on Episode 163 of Inuyasha. Her first work as a character designer was for Lucky☆Star. She has also worked on anime such as K-ON! and Tamako Market. In 2007, she illustrated her first light novel, and since then, she continued to do it for many works on the market.

Horiguchi's last credited work at Kyoto Animation was as the character designer and animation director on Tamako Market in 2013. Since then she decided to become a freelancer and work on different projects of anime and mainly as an illustrator of light novels.