married to one's work; work is one's lover
A set phrase describing someone so devoted to their job that it is like a romantic partner. Often used humorously or self-deprecatingly.
He is married to his work; he's at the office even on holidays.
When asked about hobbies, I replied, 'My work is my lover.'
仕事人間 is a noun for a workaholic person, while 仕事が恋人 is a phrase describing the relationship with work as if it were a lover.
ワーカホリック is a loanword for workaholic, more clinical or direct, while 仕事が恋人 is a metaphorical, slightly humorous expression.
A metaphorical phrase combining 仕事 (work) and 恋人 (lover), literally 'work is one's lover'. The exact origin is uncertain, but it reflects a common cultural trope of extreme dedication to work.