To be a Childhood Sweetheart that You will Regret for Life

I was once reborn as the protagonist of a crappy galgame, only to meet my end by overworking myself to death trying to save the world. But when I opened my eyes again, I found myself reincarnated once more—this time as the female protagonist in the sequel. Determined not to become a wage s*ave again, my familiars, who shared my disdain for working overtime, came up with a cunning plan.
By becoming the childhood sweetheart of the original male protagonist, creating perfect memories together, and deepening our bond through our youth, I could turn him into someone who couldn’t imagine living in a world without me…
Familiars: Now, for the final step. On the night of his proposal, when the ring is slipped onto your finger, a monster will appear and tear you apart before his very eyes. This will surely leave him with a lifetime of regret.
Nagine: ???
Congratulations. You’ve created the strongest protagonist, who will now ruthlessly eradicate all evil.