All these rape comments. Are you telling me the yandere is not respecting boundaries? The yandere, of all people? And that she might not be a good person? Holy smokes, who coulda seen this coming?!
Anyway just copy the heroine's Celestia and become better than her at it. No harm in being "vulnerable" to a power that purges evil and heals. Then you'll be the greatest in the land and you can form a harem of the pretty yandere, the cute tomboy, the gloomy girl, and the mysterious Colette. There are no flaws in this plan because this is definitely a harem manga for sure.
That wouldn't make his back sore
So it must be something more