Ruby fished Mimi in Route 118, while helping a Swimmer in order to apologize for messing his fishing traps. Ruby thinking she was hideous, Ruby throw her back into the river, she kept coming after his fishing pole while Ruby kept throwing her back in. When the swimmer realized that Ruby was fishing and discarting Feebas away he explained that, while not knowing the reason Feebas was very valuable. After learning that, Ruby tried to fish her once more, but was unable to do so. Mimi reappeared when Ruby and the Swimmer were being attacked by Zangoose and Seviper, to return Ruby's PokéNav and ended up protecting the them from the two enraged Pokémon.
Seeing that Mimi had protected them and got a liking of Ruby, the Swimmer forced Ruby to keep her. Ruby initially intended to release Mimi as soon as he had the opporunity to but latter decided that using such an ugly Pokémon to win the Beauty segment of Pokémon Contests would be a good test to his Coordinator skills. Mimi eventually won both the Vendanturf and Fallarbor contests. Ruby decided not to use Mimi when challenged Wallace for an unoficial contest, however.
Ruby used her again in the Slateport contest but, by Wallace's request the judges all voted against her. Ruby, frustrated by Sapphire's words during their last meeting, unsleashed his rage in Mimi, saying she didn't deserved to be in his team and kicking her out of it, although he realized soon after that he was wrong to do so and tried to get Mimi back, but she was gone already.
Mimi later went all the way to Sootopolis City in order to reunite with Ruby. She was then hurt and humiliated by Archie and Maxie who said such ugly creatures didn't deserve to exist, but Ruby realized Mimi's inner was greater than any external beauty and, after receiving the Beauty Contest Hyper Rank Ribbon from Wallace, gave it to Mimi and finally gave her own introcutionary speech. Mimi then evolved into Milotic, the Pokémon Ruby has been seaching for since he met Mr. Briney and helped in the battle against the two leaders. She later won the Master Rank of Beauty contests.
She was also used by Ruby in his battle against Emerald in the Battle Dome, but she was defeated by his Sceptile.
Moves used
