The Country Maiden: Fields and Leisure - Chapter 61 - Treat Oneself as Dead

The story is about a boy entering high school, who answers a strange call from a public phone one night. The caller challenges him to a bet: She’ll remove the birthmark which he sees as the cause of so many problems, and he’ll have fifty days to win the heart of a girl he’d considered far beyond his reach. And with this, a very strange summer begins.

Liu Duo was a young girl whose grandmother sold her to four brothers with the intent to be a bride. Unwilling, she ran away the following night, only to fall unconscious while trying to get away. Unexpectedly, however, she was reborn with the spirit of a 25 year old woman, also named Liu Duo.

- Description from Novelupdates

Mason was a mercenary, until the day he died on a mission after being betrayed by his unit.

Our protagonist was a Mexican who died on a flight, when he woke up he found Apollo who reincarnated him as the grandson of Gaius Octavian Turino (Augustus) the first Roman emperor, having a mission in hand to conquer the New World to save the Roman polytheist world and his existence.