OK, some questions and comments.
First, it sounds like a fun class to play.

OK, pleasantries... check. Lets go on.

Henshin (Su)
Looks nice and fits.

But one, the blind effect is connected to light not mind affecting spell- I would say the save would be either fort or reflex (you endure the flash or you managed to close eyes or something like that).

And two, 1r/lvl is good... later. Imagine 1st level character, which spends 1 full round changing, then attacks once... and goes back to being semi-useless (semi because he still has some manuevers, but looses his 'summoned weapon' which is somehow useful)

Rider Effect (Su)
Interesting, but paralyze from electricity part is too much, go for stunned (don't give players easy ways to make coup de grace)

Clash of Virtues [Suit]
If the opponent attempts to resist the challenge, they must make a Will save (DC 10+1/2 Sentai level+Cha mod). If they succeed, they are not pulled into the clash, though they take a -2 morale penalty on all attack and damage rolls. If they fail the save, they are pulled into the challenge, taking a -4 penalty on all attack and damage rolls due to how easily they were forced into the fight.

I don't really like this one, it is best if someone doesn't try to resist, it is the only way to avoid penalties.
Second problem- duration of penalties- 3 rounds, until he hits Sentai, till the end of encounter, till he dies of old age? (last one is a joke...)
The penalty even if you pass the save is a bad thing, unless it is short duration type.
The penalty for failed save... I would make it more like inability to make AoO, or make penalty lower... or make it till he hits sentai, ... or at least change the reason, typical is 'was ashamed that he hesitated' or sth.

Last one here is a question, what happens if 2 Sentai try to challenge 1 enemy, does he get -14 to attack for all enemies?

Sentai Knight [Suit]
Fine one, would think about heavy armor (mech?) as an upgrade that you can take later.
Cosmetic change, instead of 'he summons shield' I would make 'gains ability to summon shield' ... why hinder the 2-h guys...

Last one:
Heroic Speech (Demotivate) [Suit]
While if we assume that the penalty would stay around -1 to -5 it is nice (later in the game because the possible -4 on 1 lvl is a bit scary)
it become bad when we consider high charisma types... -15 penalty without a save? ... would be bad
I would make it a set penalty/ limit the penalty to for example 1/2 lvl/ give the poor guys a save. Also is it fear based?