I think there are at least 3 games on F95 that have 'death note' as their base if i remember right.
Grind would probably be boring.. unless it's some kinda fun type of grind.
Maybe something like... mc needs to get himself horny by imagining things with the girl without her noticing (in close proximity to the target girl he needs to do things, sexy things).. and if he succeeds in doing that he then can transfer that horniness to the girl via the book?
And as that horniness accumulates over a few days.. she can then succumb to it and jump mc...
That's what at the top of my head atm.