I've been looking around some IPTV providers who have Japanese channels but haven't got any success. Japannet IPTV and Forjoy TV have good buffer speed but they do not offer m3u link. TNT has some channels but it's too slow to be watchable.
I willing to pay up to 20$ per month so anyone has any suggestion please leave a comment below! Thanks you guys so much!
Fluxus has some channels and so does www.king-iptv.net I don't know if and how they work though, you need to check it yourself. But the choice is limited and you probably won't get the channels you're after. Better stick with the aforementioned sources (isakura is also a similar provider)