Felix is known to be a very kind hearted and soft spoken person. His appearance gives off an intimating person, while in reality, Felix is pretty quiet and a soft-spoken person. He is stated to have ADHD (Attention Deficit Hyperactivity Disorder), Felix is shown to have a hard time in school and focusing all of his attention in classroom, while he is seen off doodling something in his notebook or daydreaming, Felix is very easily distracted which makes it hard for him to study and stay focus on school activities, stated by Tsuta, he seems like an extremely smart kid, but he has trouble paying attention in class or doing his own classwork, which makes him fall behind a bit in his studies, which makes his peers and friends a little concerned about him. He is also shown to have a hard time just making friends or talking to people as he has anxious thoughts that leave him unable to want to go make new friends, because he doesn't see much of a point in making friends when most of his other ones have very complicated relationships. Felix can tend to let his emotions get the better of him if he isn't paying attention, which also makes it hard for him to talk to people, as sometimes his emotions get the better of him, which gives people the wrong idea about Felix as a whole, which he doesn't want that, but it's hard for him to control those emotions he has.

Felix when he is focus, is very serious and quiet, and tries his hardest to make sure nothing distracts him, he always sets his heart out to do something, and forces himself to try to get something done. He is also obviously very passionate, he can get into very long conversations about his own goals and accomplishments he wants to reach in conversations, which shows people that he's passionate about his goals and that he is obviously kinda talkative when he isn't paying much attention. Felix has a very wide imagination too, always imagining very wacky and funny situations in his head, or stories, which he always tends to daydream about when he is, he often will get lost in his own thoughts, thinking about what if he lived in a fantasy world, or what if he lived in some anime he liked. His daydreaming always happens, and you can normally find him daydreaming if he isn't talking at all. He tends to write stories about his daydreams, and when he does daydream, there is a chance he might just fall asleep randomly because he gets tired.

Felix when he's having an off day, is just overall, very sleepy, and can be found sleeping in some random position, Yami and Inari both stating they saw him leaning on a wall, asleep standing up, Inari was confused on how that was even possible. Most of the time you either find him extremely sleepy, so this is a very often thing, but most of the time when he knows he should sleep, he does sleep and have enough energy.