Velmoria

"Any vampire who eats a human will be killed by the Velmorias..."

To marry his vampire girlfriend, Yuto decides to become a vampire himself. Just as he thinks it's time to cue the wedding bells, she tells him there's one absolute rule he must never break...?! Meeting the most feared sister-and-brother duo in the vampire world is about to throw his life into chaos!

(Source: MANGA Plus)