This sub scenario won't appear in Florem for a little while after you arrive. To trigger its activation you need to complete the fetch quest involving Sage Yulyana, which means trekking through Mount Fragmentum - and then back again. Once you do, the side quest will be activated in Florem's main plaza. (I don't know if the entire sub scenario is available before the beauty contest is completed, so you might as well get it out of the way before proceeding with the quest.)
- You'll find the man in red in the main square of Florem. Talk to him to set the side quest off. He's kind of a creepy booger.
- Head to the inn after speaking to the guy. Ringabel will mull over the problem of 'techniques'.
- Return to Florem at night and search its northern quarter. 'Red' is waiting Approach to spark another cut scene.
- Jump to daytime again. Red only seems interested in nighttime strolls, so leave Florem and muck about until the sun sets. Head back to the northern quarter once it's dark. Make sure to save this time.
- Speak to the young red-headed woman south of Red. She'll freak out and run away. After she's gone, walk up and confront Red yet again. Off he goes... (Make sure you speak to the girl first. Otherwise this scene will just keep looping.)
- The cut scene continues. Oh, Edea, what were you thinking?
- Edea and Red will disappear, though you'll get a hint of where they've gone. Then you'll wind up beneath the street.
- Cut scene continues. What a surprise, Red - no, sorry, DeRosa - is up to no good. After a long chat you'll wind up in a battle with the dandy.
This is a brutal battle. Befitting his status as a Red Mage, DeRosa is capable of a multitude of actions. Most damaging to your team's HP is his magic and his normal physical attacks, which typically get used multiple times in a turn and can inflict quite a bit of damage. He also has Revenge, so your hits will help replenish his BP. Yeesh. Thundara is his attack spell of choice, and he'll use it constantly. He can and will also heal himself as you're damaging him, and will regain a substantial amount of HP each time. Yeouch.
Nevertheless, it's not his standard magic that causes the most trouble to your team, it's his status effects. You'll begin the battle with Edea inflicted with a charm effect that will make her worse than useless to your party until it's healed, and he'll keep using his Captivating Cologne attack to ensnare the rest of your party. If left to linger, charm status can ravage your party. Remedy or Esuna this status as soon as it hits you. His other status attack is Fear, which will block the Brave and Default in options in your characters; this, too, needs to be healed immediately. One character on item or healing duty at all times is highly recommended.
Though DeRosa doesn't hit that hard, this battle is difficult simply because it takes so long. Stock up on a lot of restorative items beforehand, and absolutely dedicate one character to healing everyone else while they wail on DeRosa. Don't let up on healing status problems for a second or they'll demolish your chances of beating this guy.
- After beating DeRosa you'll gain, yep, you guessed it, the Red Mage asterisk. This will allow you to assume the Red Mage job, which is very handy for more diverse characters who want to use a healthy mixture of black and white magic simultaneously. Red Mages don't gain every black and white spell available, but the ones they do learn - as well as their innate melee combat abilities, above and beyond those of other mages in the game - make them valuable characters indeed.
- Almost done. Before leaving DeRosa's luv den, check the cylindrical statue just down from the weird bath thing in the middle of the room. It contains a Bomb Fragment.