Ore no Kanojo wa Sekai Isan

World Heritage Sites (Sekai-san) are proof of culture and civilization that mankind should inherit. However, for several years, the mysterious phenomenon that ordinary girls and their world heritage sites link their existence has occurred frequently all over the world. Waku Santaro enrolls in Yggdrasil, where these "heritage girls" are gathered, and they have special abilities that embody world heritage. There, he is reunited with Sakurada F. Milia, a girl with whom he once had a heart-to-heart talk. "I've become the Sagrada Familia!" Santaro, surrounded by the girls of legacy who are not easy to deal with, searches for a way to turn Milia back into a normal girl. Then, a mysterious heritage girl appears and attacks Milia. ... An unprecedented battle of different abilities is about to begin!

(Source: Shueisha, translated)