To give the two a sense of connection the ML is actully some kind of nine-tailed cat, anyway ML was helped by MC in one of those worlds and to help back ML bound MC to the system to let him survive. So MC's kindness that is present throughout the whole book is also the reason for him being helped by ML.

ARCS (if you'd like some spoilers) :

1. Swapped babies, MC arrives in time not to be taken back to asylum where he was sent by "fake" master's relative, escapes with a group of young men and become a master of traditional Chinese medicine.
2. 80's. MC is a cook in a restaurant who has 7 sisters. But has a twist about his birth and why all 7 sisters act like they want to ruin MC.
3. Twins. One is taken away by the mother another stays with abusive father. MC is stuffed into worst class, he takes it upon himself to make everyone in the class excell in their field, he himself strives for the first place to be interviewed and reveal the truth about his family and this class. Also has neon green hair.
4. Metaphysics. Quite twisty situation where MC's sister wanted to be a wealthy madam, but her marriage is unhappy, also in this family no one is a biological child, one is the son between a wife and metaphysics master who feeds luck of others and sacrifices for his son's success.
5. Veterinarian. MC is a pro in the field, while protag has an animal system, basically uses animals for success, but does not love them and holds them in anti-sanitary conditions, which is uncovered by MC, weird arc, even ML is a Maine Coon.
6. Entertainment. Boy group with MC should have been most successful, but because of a reborn person with a system they always get inexplicable songs etc. MC turned the tide and allowed them to succeed.
7. MC's research was stolen, but no one in the university believed him, he quit and joined the research lab with another person, his mentor, who had similar experience. MC became a big person in the end
8. Weird story, because OG is hoosexual, married a woman who also liked same-sex, but they used this marriage as a shield, OG got into accident, wife was worried her child will be taken so she left, OG believed that his wife and daughter died. MC becomes teacher of his biological daughter and gets closer to her to slowly tell her that she was not left alone or abandoned. But honestly, why he couldn't just say it directly and use time to warm their relationship.
9. Very random. MC is a bartender, his reputation was ruined because of his brother who wanted to show off and pretend to be someone else. MC made him admit the truth and apologize. ML in this one loses his sight and is coveted by people. What I found ridiculous is how many people were planted and all of them had a handle (like naked load etc.)
10. Ancient plane. Framed family, MC becomes a taoist monk. To prevent the world from being tormented MC seals female protag's soul and system, otherwise the world will turn to chaos. He also brings up the heir to the throne and the dynasty changes when Emperor is dethroned.
11. MC has a sister who was adopted while he stayed in orphanage. She turned into a people-pleaser, had very submissive personality. MC arrived in time when her fiance and her bestie had an affair, he forcefully took her away and started to "train" her so that she would change her temperament. ML is also a big figure in this world, eventually this girl succeeded both of their businesses. FIrst time MC promises ML to be engaged in next life (his lifespan was short in this one)
12. Last arc, in which MC finds ML being imprisoned by a family, they made their son impersonate ML. So MC saves ML and uncovers a trafficking family.
13. They return to original world before the accident and come together.
    
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