Had the same feeling when it was my first time I listened it. Apparently it was known as "false nostalgia". It occurs when elements in the song resonate with cultural or musical references that create a sense of déjà vu. Try the OST, I had the feeling of nostalgia & happiness when I listened it in Japan.
Oh, that's an interesting perspective. I'm a fan of reading VNs with wordless, melancholic OSTs similar to this, so this song might remind me of those (Though I think this is my first time feeling oddly familiar with a soundtrack I didn't know. )
Not sure if this is the answer you're looking for. It's from the 2nd chapter known as "Edo Kyuushin-ha Hen" ending part. for more info. vndb.org/v11157 vndb.org/v12260
+jetairliner spartan I haven't played the fandisc yet. but I think no, that's probably not Yasuube. Because the setting is always on Japan past time Edo period. Maybe you had seen someone who are similar to her, example like Grisaia？
