There are quite a few Skills you can obtain and unlock, thankfully none of them are missable. However, you may want to increase your friendship meter with a few of the individuals first.
Anyway here is a quick guide on how to unlock every available Skill in the game and how to get each one.
Onodera sell quite a few of the Skill Books. However, you need to befriend him first to unlock all of his gear. You can find out how to befriend him here: Befriend Onodera
Rush Training: 560Y
Secret Technique (Reverse Beatdown): 650Y
Secret Technique (Front Beatdown)
Secret Technique (Front Beatdown) can also be found during Chapter 12 in Monsieur Lee 2F
SKILL UNLOCKED: Ex Boost Lv1 (L’Amant)
This one can be purchased at L’Amant for 1.5k Chips
SKILL UNLOCKED: Re-Guard (Dragon Palace 2F)
This one can be purchased at Dragon Palace 2F for 1.5K Chips
SKILL UNLOCKED: Danger Display (Dragon Palace 3F)
This one can be purchased at Dragon Palace 3F for 1.5k Chips
FRIEND OBTAINED SKILLS
DICE & CUBE
Some skills can be obtained via the VR Dice & Cube game.
SKILL: Resolute Counter
INFO: It is found in the Middle Course (Challenge Rule)
SKILL: Ex Running Palm Strike
INFO: It is found in the Long Course (Normal Rule)
SKILL: EX Running Assualt
INFO: It is found in the Long Course (Challenge Rule)
Related Guides / Links