I don't care enough to search for Chemtrail though. He's not even related to the other demons.
Was able to find and defeat Matador and White Rider in about an hour and a half.
Matador is actually fairly easy to take care of if you know what triggers his Almighty switch.
And when that switch turns on, Matador becomes a whole whole lot harder.
Because he blasts you with Anticuton and Energy Drain more than once each turn. And unlike Red Rider, he isn't going to accidentally end his turn with an elemental attack.
Yet if you just have one party member that does not have resistance to Physical, he simply repeats using Taunt and Sukuajya to lower your stats and increase his, and then attack with his basic attack a few times.
And when he does his physical attack, he doesn't necessarily home in on that one party member without resistance, so he sometimes can waste a move by attacking someone with resistance to his basic attack. In my battle, I just used my Masakado. I was able to take out Matador just in time, right after Masakado was defeated.
However, one thing to beware of is that Matador's basic attack has a chance of striking more than once. And if you aren't careful, he will get a Critical -> Grin, which only leads to another critical and more, which can be pretty nasty.
White Rider was also surprisingly easy. Maybe Red Rider was just too hard.
Red Rider just loves to power himself up. He will boost all of his stats twice, use Concentrate, and after all of the buffing, he finally attacks once or twice.
It seems he will use his party-targeting Thunder skill even if most of your party negates it, so it helps a lot to be able to reflect or absorb his powered-up, very powerful Thunder attacks. If you have three members that reflect, he receives over 300 damage per reflection for a total of 900+.
Of course, you should have a demon that removes his stat boosts. I brought one from my demon-dex (Shinigami Nelgal), but I just realized I forgot to take a picture.