Okay, I did give it a try.
First fight, I got surrounded and couldn't do anything except escape within seconds.
Viewing post in Streets of Ryona ( hentai streets of rage version) comments
Oh I see, well in that case you need to learn some combos with the specific character you pick, like "v + >+punch", or do that twice quickly for a special move. That will help you survive the waves. It's not a easy game indeed, the difficulty was adjusted for a intermediate to veteran player, but it's not hard at all.