This character is a workaholic.
A workaholic is a person who is addicted to work. While the term generally implies that the person enjoys their work, it can also imply that they simply feel compelled to do it. There is no generally accepted medical definition of such a condition, although some forms of stress, impulse control disorder, obsessive-compulsive personality disorder and obsessive-compulsive disorder can be work-related.
Workaholism in Japan is considered a serious social problem leading to early death, often on the job, a phenomenon dubbed karōshi.