Nega-Suu/Relationship

The following is a description of Nega-Suu's relationships and interactions with other characters in Monster Musume: Everyday Life with Monster Girls.

At least at the time of Volume 13, Nega-Suu was still a wild Black Slime with a possibly not fully developed sentient nature. Because of this, Nega-Suu acted mostly on instincts, which is why she interacted with the other characters but didn't have any real relationships at the time.

Kimihito Kurusu
Like most humans, Nega-Suu didn't have any particular opinions towards Kimihito at the time of Volume 13, and it's unclear if she paid any particular attention to him at all. While she was ready to attack Kimihito in Chapter 54 and Chapter 55, that was mainly because he was in the way of her intention to absorb Suu and she probably wouldn't have taken much notice if he was killed in the process.

Kimihito on the other hand was genuinely afraid of Nega-Suu, but in order to protect his girls he was willing to fight the giant Black Slime and finally defeated her with Suu's help by sucking up Nega-Suu's core with a vacuum. It can be surmised, not least because he himself and Suu nearly died in the process, that since this incident, Kimihito has devloped a deep dislike for Nega-Suu, as she was also one of the most dangerous Liminals he has ever encountered.

Meroune Lorelei
Nega-Suu and Mero didn't meet during the events of Volume 13, as Mero was at the Kurusu house with Papi during the incident. However, it can be assumed that Kimihito and his other household girls told Mero about the incident and Mero has since developed a dislike for the Black Slime as she almost killed Kimihito and Suu.

Hot Spring Slimes
After the Black Lily Laboratories discovered through their research that Slime has high filtration capacities, they used Nega-Suu as a living water filter for the filtration system of the Arctic Inn. Unbeknownst to anyone, however, Nega-Suu came into contact with the DNA from various Liminal species bathing in the onsen and used this information to multiply herself and create dozens of new Slimes. While the hot spring Slimes can theoretically be considered as Nega-Suu's children, it is unknown if she has any (and if so, what) relationship to them.