The Heroes of Domino(DISCONTINUED!WILLNOLONGERUPDATE!)

Domino city is in danger, the evil Marik sends out monsters to drain its citizens energy. Luckily the city has two magical boy heroes who defend them from these monsters. Secretly Yugi and Yami are these heroes, they transform using their puzzle necklaces and use their powers to banish the monsters

After some defeats Marik comes up with a plan, whilst the two heroes are fighting one of his monsters, he casts a spell on Yami without him noticing. This spell slowly drains his powers, he starts to involuntarily transform back into his civilian form at random times, other times he can't transform when he tries, as this happens, he starts to get weaker and weaker and Marik gives Yugi an ultimatum, give him both millennium puzzles in exchange for Yami's life.

This story was suggested by @B00100806
The idea was theirs, not mine, and the art is not mine either.