The first area should be pretty straightforward. About the most difficulty I could see happening is getting that Jacky on the left without unintentionally hurting or killing yourself.
Bomb Up, Fire Up, Speed Up x 2, Clogs, Heart
Jacky x 4
This introduces a new enemy, Eyti, and has a lot of vertical platforming. The Full Fire can come in handy.
Bomb Up x 2, Speed Up, Armored Jacket, Full Fire
Jacky x 4, Eyti x 1
Lots of gates here. Don't bomb the blocks with the spikes in them, for obvious reasons, and try to hit the far left Jacky without hitting the block he's on, or else you'll have lost a very handy Remote Controller.
Bomb Up, Fire Up, Speed Up, Full Fire, Remote Controller, Penetration Bomb
Jacky x 4, Eyti x 2
Those generators occasionally shoot deadly waves between them, so be careful. Thanks to the wonky camera, those Eytis on top can kill you if you're not careful.
Bomb Up, Fire Up, Speed Up, Penetration Bomb, Armored Jacket
Jacky x 2, Eyti x 3
A huge tree, Torent unleashes caterpillar minions that transform into moths. Watch out, these moths will attack!
Torent / トレント can be difficult if you don't have many Fire Ups or lack the Remote Controller (or to simplify, if you used a password to reach here). He flies along after you, occasionally stops to shoot bullets in four diagonal directions, or to deploy two caterpillars that crawl along the floor and shortly become moths that flutter to the top and off the screen.
When you hit him once, you can stand on that left platform and keep planting bombs and he'll get hit by them every time, granted your blast radius is long enough. Requires 5 hits to defeat.
ITEMS: Bomb Up, Fire Up, Speed Up