These are the various relationships Meroune Lorelei has or had over the series.
Humans
Kimihito Kurusu
Mero first meets Kimihito after he saves her after Mero looses control of her wheelchair going down a hill. She later joins the Kurusu household and have a strong desire to become Kimihito's mistress and wants to be in a tragic relationship with him. Her will to have a tragic relationship also causes Kimihito to almost drown. After the events at the Mermaid Kingdom, Mero ditches the idea of being Kimihito's mistress, wanting to be his wife instead.
Kuroko Smith
Mero respected the Interspecies Exchange Coordinator Smith as an authority figure as well as treating her in a formal, polite, and kind way like she would to anyone else. Initially, only Smith knew Mero's royal social status.
Kasegi
Mero initially felt uncomfortable when Kasegi was filming when her top was slipping. After Suu blew Kasegi's cover, Mero along with Miia and Centorea became angry towards Kasegi. Mero was going to attack Kasegi with a large sea shell but Kimihito attacked the con man instead.
Ren Kunanzuki
Mero was kind to lend some of her clothes to Ren Kunanzuki whose school uniform was stained from Miia's food. However, Ren insulted Mero's clothing as "embarrassing".
Fellow House Guests
Miia
Mero wants nothing more to be Kimihito's mistress and has set her sights on making Miia become his wife. However, lately she's started to become unsatisfied with becoming the mistress and has now announced that she wants to be his wife and to make Miia his mistress.
Papi
She doesn't seem to interact with Papi but shows respect to her.
Centorea Shianus
Mero initially thought Centorea to be the master's lover throwing the centaur off guard. Mero respected Centorea's loyalty and devotion as a knight to their master especially when she unwittingly projected her royal aura causing the centaur to think that she was standing before royalty.
Suu
She doesn't seem to interact with her much but does seem to respect her.
Rachnera Arachnera
She seems to respect her but not much is known as they never interact with each other. She secretly likes the feeling of being tied up by her.
Lala
They didn't seem to like each other at first but later respected each other after the explanation by Ms. Smith.
MON
Doppel
Tionishia
Zombina
Manako
Monster Community
Polt
Draco
Miia's Mother
Papi's Mother
Centorea's Mother
Yukio
Liz & Kinu
Potemkinme & Sabastian
Oct
They became friends and worked together to help Oct.
Meroune's Mother
They are mother and daughter.