Decided to give this one a try even though I knew I wouldn't get far. I'm terrible at platformers and can't handle bullet hells at all, and this is both... the first enemy took me four continues. I scummed my way forward a bit but gave up after my eyes started hurting.
I think this might be the most refined Tengoku yet. It's a gaiden game, but it feels more polished mechanically and better presented than Tengoku 3 from the parts I played. It's definitely an established series at this point, with the same style and a lot of consistent details. Just a little improved every time.
The only thing I felt was a flaw was that the tutorial level really rushes along; as soon as you try what it's telling you to do, even if it was by accident, it moves onward.