口笛少女

On these albums

Mana-Khemia Original Soundtrack中河健 & 阿知波大輔 · 2007Soundtrack

ガスト20周年記念CDボックスVarious Artists · 2015Soundtrack

Source: MusicBrainz recording a57f1138-5f6b-460f-9ef0-51bf8b11a17b (CC0).