Well, I had to do a lot of digging to find these:
https://www.youtube.com/watch?v=n1qqwQveYv8
https://www.youtube.com/watch?v=IKjIIU3aDg0

^ I believe that the acts in these 2 links are submissions for a competition specifically targeting younger musicians. There's a lot more in the related videos list if you want to check out more, or just pm me.
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now, these ones are a lot more predictable in the whole jpop genre, but they kinda grew on me for some reason:
https://www.youtube.com/watch?v=GJjqj56A0p8
https://www.youtube.com/watch?v=78eFtdGce0Y
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lastly, I'm not sure if it counts as 'jpop', it's labelled as enka, but it's very good and i listen to her quite a lot:
https://www.youtube.com/watch?v=_b6IWXKO5dQ
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p.s. this is a kpop band, but you might like them since they sound a bit like Soutaiseiriron:
https://www.youtube.com/watch?v=rvrWb-5hdoM
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p.p.s. I forgot about these:
https://www.youtube.com/watch?v=IjE3SJTQIB4
https://www.youtube.com/watch?v=-DZuJWfPzJE
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ok i'll stop now

Thanks dude, I'll check these out definitely. The first one you linked especially