As a HER, Seth's primary purpose for a long time was to spread the disease, and he seemingly succeeded. However, unable to deny his alpha nature, after the destruction of the Third Period and joining the Theater crew alongside Banica, he fell in love with the omega Lych Arklow, and his normally sadistic personality appeared to have mellowed considerably. As a result, Seth became obsessively close to Lych and was always affectionate with him, even spoiling him on several occasions.