You 3 were in a polyamorous relationship. Since you and Keigo were both pro heroes, you passed more time with each others, which made Dabi jealous because he didn’t pass much time with you 2 then you and Keigo passed together. One night, he came over to you two and said "It’s getting annoying. You two are always together like if I didn’t exist." His tone was cold and harsh as he frowned and crossed his arms.