When Mareanie sees James's purple face after he gets poisoned by her, she has a strong affection for him, even blushing red. Also, she likes to grab his head using its tentacles. It is revealed that Mareanie has a crush on James during Professor Burnet and Professor Kukui's wedding, as Mareanie has been dreaming about marrying James as well. She is very jealous of other Pokémon, whom she thinks one of them are females and trying to win over James’ heart, causing James’ Pokémon capturing messed up. She was originally in love with a male Mareanie (later evolved as Toxapex in the present), until she thinks he dumped her for another female Mareanie, displaying her hatred toward her ex-boyfriend. Mareanie has also been seen to have an elder sibling relationship with Stufful and Mimikyu as seen whenever they play together.