I've never been able to get over how perfectly this op complements DR3's despair arc. If you're going into DR3 from the games you're watching the Despair arc with an insane sense of dread, you've got mixed feelings as it's presenting you with this happy-go-lucky slice of life-style arc with the characters you know and love from DR2 and it makes you feel fuzzy watching them do their thing and be happy, but you also know that something beyond awful is going to happen to them by the time this series is over, and you're just waiting nervously for things to take a turn for the worse. And the op reflects this, it's all in washed-out pastel colours that aren't quite happy or unpleasant, but it's all presented in a way that makes you feel uneasy, all with this haunting song in the background which is also simultaneously cheerful and eerie, but not in an overblown way. Then as the series progresses and the things you've been dreading start happening, the op's colours change and become darker to reflect everything that's going on, and without doing much aside from that the op goes from rubbing salt in your unease to becoming almost a traumatic event in itself every time it plays. God I love this series.