Petals of Reincarnation

Touya Senji has spent his life trying and failing at every skill he has ever picked up. The new transfer student Haito is the opposite — a teenage kendo champion with national-level wins under her belt — and she also happens to be the current holder of the Stem of Reincarnation, an ability that lets her tap the talents of her past lives at the cost of cutting her own throat each time she invokes it. Haito does not need Touya to become a swordswoman. She needs him because his lack of talent is the only neutral container the Stem can pour an ability into without destroying the new host.