This was a bit interesting. Definitely a very 'shonen' feel, including the deus ex machina style "I'm going to be stronger now because I feel like it".
The first battle was kind of annoying. At first it sounded like you were expected to keep the resist buff on until I experimented with it and realized I can just use the resist when the state is applied. The fight is also extremely long. It felt longer than even what should have been the longest fight.
The boy's ultimate skill is just unbelievably weak. It does maybe 4-8 times the weaker skill and costs 10 times as much with a buff state? One of the boss fights mentions being able to finish the fight in one hit. Not true because the ultimate doesn't do that much damage.
The story was pretty obvious the moment you meet certain characters. The game doesn't hide their role at all. This may be fine given that this seems to be a very shonen genre game, but I just wanted to point it out in case that wasn't the intention.
For one of the fights, there is a bit of an infinite loop where you can just effectively max your resources at will.
One of the fights felt a bit annoying because... if there is only one enemy, there is no real need to make us select the enemy, you can make that selection automatic.
Also, the wording regarding multiple weapons is a little bit unclear. That could have been made somewhat more clear.
It is very easy to accidentally select the default choice when clicking through dialogue and considering the long dialogue, it might be nice to have an option to save before the fights.
One of the enemy looks weird with dialogue though because there is a gap in the image instead of being seamless. You could fix this by either having a second image that appears/disappears over the first image when dialogue is present or by having the image extend to the edge or have the image naturally fade away.
For the multi-part fight, the second fight feels a bit weird because it looks like you are fighting the head.
Might be worth using a spellchecker and maybe a grammar checker.
For post-game, might want to add a cancel option instead of making someone press ok 18 times to exit. You can do that using a few different methods, but might want to use something.
Otherwise, the graphics were fine. The attack sprite animations felt a bit weird since they only show up during attacks.