That's right guys. Turns out there IS a secret boss in Re:Coded named Bug Roxas. Who seems to be a little bit stronger than the final boss Roxas fight. Bug Roxas has four phases in the fight:

 

His first is a "blue" phase. It is the same as his final boss form, he'll have boosted defense. Next is the "yellow" phase, where he'll become about 3x faster. You'll want to get rid of it quickly. Third phase, the "red" phase. He'll becomes unflinchable and deal 2x more damage than usual.Then, the final phase, the "green" phase, makes Roxas a giant and doubles his HP bars.

 

 

After the fight, you can buy Ultima Weapon, a Debug Code Y and +2 stat panels.

 

Here is the link to the Bug Roxas boss fight.

Wow nice find

cool, not only do i finally get to fight roxas, but i get to do it twice

Great find!

Nice! But after watching it, I'm thinking, what's the point of doubling his HP bars if he stays at the same HP? It doesn't go back up or nothing. :S

Awesome!! I'm pretty glad that this game will be out in a about 3 months!!

Nice find!

cool, not only do i finally get to fight roxas, but i get to do it twice

 

~ Five times

Where and how can i fight the bug roxas?

After beating the game go to hollow bastion and select free quest, i think its the top option. Then go to the upper level of the lobby and thene there should be a new system area in the middle of the chandelier. This is the hardest SA in the game. The enemeis are super buffed, the challenges are crazy, and you have to go through 13 floors. The 7th floor is a fight agaisnt one of those bug block snake things and the 11th floor is just an onslaught of 99 shadow bugs. Also if you get 1500000 sp in it you can get Ultima Weapon.

Nice find man ^^