Sein is an infiltration-type cyborg built sometime after Quattro. Her signature ability—the Deep Diver "IS"—lets her swim through solid matter like ground and rock as if it were water, making her uniquely suited for underground or covert ops. She's also equipped with a Periscope Eye in her right index finger, a cybernetic tool that functions as both an extra eye and a device for cracking electronic and magical locks.
What makes Sein stand out is her personality. She's surprisingly upbeat for a combat cyborg, though there's something inherently shifty about her vibe. Despite a track record of failures, both Scaglietti and Uno value her heavily—her "IS" is complete and independent, which is rare among the Numbers. Positioned right in the middle of the creation order, Sein naturally falls into a mediator role between her older and younger siblings. She and Wendi have a solid relationship, partly because they share a similar cheerful outlook and partly because Wendi was once her student.
Content compiled by AnimeList.moe from publicly available sources.
