Noa Noa - One Summer Love.
The album where this comes from, アジサイ, is great as a whole, but this one in particular stands out to me after a few listens. It just hits that perfect balance characteristic of early 2000's Japanese music (Shibuya-kei, specifically), not too fast, not too slow, jazzy, poppy, melodically interesting. Noa Noa sings in both perfect Portuguese and Japanese in this album, which makes me wonder about her origin and life story. Again, characteristically for many Japanese singers, I searched for and found nothing else apart from this album and passing references to her existence in other Shibuya-kei songs.
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Song:
https://www.youtube.com/watch?v=Mktu8PJbuYU
Album (Highlights, IMO: 05, 06, 08, 09):
https://www.youtube.com/watch?v=lN0b6vRKdlE