At first I was thinking what similarity you could find between BoY and Uso... Then I realize you're talking about the music in the beginning of Uso and the music after the beginning chorus in BoY. Yeah melody is similar but the feeling is different. In BoY that melody sounds desperate... in Uso it sounds like hikki's about to scold someone (although I've never read the lyric in Uso
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Simple and Clean sounds like Uso because the music in Simple and Clean is the original melody when hikki first composed the song. When she wrote the japanese lyric of the song (which is Hikari), she couldn't fit the words into the music, so she changed the music of the chorus. She felt "bad" about that (ahh I can't really remember what she felt) so she made another song to fulfill that part of melody, which is Uso
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