Does it have to be human?

Seymour can best be described as the sweetest murderer you’ll ever come across. Even at his current canon point of killing a guy, he doesn’t exactly enjoy the idea of killing people, even if he thinks they “deserved” it

In his heart of hearts, Seymour is a good person, or at least he tries to be. His kindness and gentle nature towards others is completely genuine which, while it’s shaken by the murder, has not been shattered by this point in his canon.

In fact, his kindness is actually what gets him to kill in the first place. While he is tempted by Audrey II’s offer to kill in exchange for fame and fortune, he still refuses to kill anyone until he sees a man being abusive to someone he cares about

At no point, however, does Seymour seem to enjoy the killing. Even though he’ll attempt to rationalize it to make himself feel better, he is very clearly traumatized by the murders and knows not-so-deep-down that this is wrong.

Despite how much of a genuinely good guy Seymour is, he is also a little selfish too. Not especially for riches and fame, but for affection. Because Seymour is so starved for affection, he tends to do questionable things just so he doesn’t lose them. This is especially evident in the full version of the song “The Meek Shall Inherit” (this takes place after his canon point, but the song details Seymour’s fatal flaws greatly). In the song Seymour states that he doesn’t care if he’ll be a nobody again, he’ll kill Audrey II just so no one else has to die. However that plan is changed because he realizes that he’s terrified that Audrey would dump him the moment he lost his money and fame and implicitly agrees to kill more people just to keep her around.

But even more than his selfishness, Seymour’s fatal flaw is that he’s too meek. Even if he is completely aware that something is not right or if someone is asking him to do something he absolutely does not want to do, he will still end up saying “yes”, either because he’s afraid of the repercussions of saying “no” or he rationalizes that “well, it really can’t be that bad, can it?” And even then, judging by the “The Meek Shall Inherit” song, even as he rationalizes it, he knows that whatever he’s uncomfortable about is wrong.

Similarly to being meek, Seymour suffers from a horribly low self image. This comes from his caretaker treating him like crap from a young age and growing up in a rough environment with little companionship or love. From a young age, Seymour was forced to do labor for his caretaker Mr. Mushnik, while to this day insults him for every mistake Seymour makes, it’s to the point that Seymour is clearly nervous to make any sort of suggestion to him. Also in the song “Skid Row”, it seems to imply that he will just quietly agree with any insult someone throws at him.

This is the biggest reason why Seymour tends to be clingy whenever anyone shows any sort of kindness to him. He tends to internalize his clinginess, so this normally doesn’t come off as creepy or even super desperate. However some days he will ask friends and other close ones if they actually like him. I imagine, if he develops more positive CR in Drift Fleet, that his clinginess will subside, but it will be hard to shake him off of this completely.

Because of his current canon point, he has also become rather traumatized by his murder. Even though he hated Orin, he was very obviously troubled by killing and chopping up his body in canon that he can’t sleep the following night

At the end of the day, it’s really best to describe Seymour as “really kind and genuinely well-meaning, but he’s such a bundle of issues.