From this post:
https://humans-in-space.jaxa.jp/en/biz-lab/news/detail/005757.html
… I see that a date has been set for this deployment: 19-June-2026.
There was another post about HOKUSHIN-1 a couple of days ago, so I spent quite a while trying to locate downlink frequency information.
The only reference that I could locate seems to indicate that S-Band (freq unknown) might be the only communications mode on this satellite:
… if anyone finds out the exact frequency, or if there are comms on any other band, please share. Thanks!