Silvi

There was this manhwa where the MC had an older brother who was trying to kill him, and his mom was very partial towards his elder brother. But his grandfather preferred him, which made the mom and older brother hate him even more. MC didn't want all this trouble and genuinely wanted his brother to inherit the company so he made a pact with the ML to pretend to be lovers.

So the story went like MC got transmigrated into a book/game and he had to help (?) the ML or something. The MC knew he didn't have much time. And the main thing I remember is the MC's relationship with his grandma, in his real world he had regrets of never spending enough time with her which he tried to compensate in this transmigration. Also at one point the MC had to choose between his grandma and the ML.