Mariko Iwadate (岩館真理子 Iwadate Mariko, born 8 February 1957, in Sapporo, Hokkaidō, Japan) is a Japanese shōjo manga artist who writes primarily for Margaret and Young You. She won the 1992 Kodansha Manga Award for shōjo for Uchi no Mama ga iu Koto ni wa,[1] and her manga Ichigatsu ni wa Christmas ("Christmas in January") was adapted as an anime OVA in 1991.