“Sonatina of Hide-and-Go-Seek”
“Kakurenbo no Kosōmeikyoku ~sonatina~” (かくれんぼの小奏鳴曲 〜sonatina〜)

Yuichi and Mai continue to battle the monsters, and when Yuichi is attacked, he is shown something he should not have forgotten years ago, which are the memories between him and Mai who has a mysterious power.