
I don’t remember well but im sure the author wrote the both of these stories, and in one chapter we see a little kid go up to our mc with two parents following the kid a few paces back, in attempt to grab their kid. Once we see their faces we can tell they are the couple from “a good day to be a dog” hope this helped!

You didn't read my first reply, the flower guy has a mole near his lips, the teacher doesn't, they're different people, they just both have blond hair, it's not a crossover character
I even bother to take a screenshot of both characters
Teacher has brown eyes
Flower guy has black eyes
The eyebrows are also different
The only resemble is their blond hair, even the hair texture is different, teacher has straight hair, flower guy has wavy hair
wait what? i read some comments telling that the boy with a flowers is also a character from 'it's a good day to be a dog' which also remembers his past life (author's another works)