Sister Princess - online puzzles

Sister Princess (シスター・プリンセス, Shisutā Purinsesu) is a Japanese seinen series written by Sakurako Kimino and illustrated by Naoto Tenhiro. It began as a serialized light novel series in 1999. In 2001, a manga series and a bishōjo game for the PlayStation were released. Sequels to the game were released for the PlayStation and Game Boy Advance. Sister Princess was also adapted into two anime television series.