The second character is actually pretty useless, because they don't level with you. That means you have to level up every additional character you want to bring with you if you want to play them. And there are a LOT of second character choices.
Problem with this game also is that there's zero incentive to stick talismans to weapons long-term. You will die, and will lose all your inventory, so it's just as easy to scavenge any weapon you find from the current dungeon and ignore the upgrade system. Also there is very little difference between this and the first Izuna, so you get the feeling of same old, same old.
It's still pretty competent for what it is, and it can be fun in a grindy way. Plus many place sell it for 19.99 US, so its definitely a good value. It's not for everyone though.