User blog comment:Dark Paladin X/Sana Futaba/@comment-32751919-20190911035642/@comment-405747-20190911204408

Yeah, she's basically a defensive support for Quick teams for challenge quests. The problem with most Quick teams is that they don't have a dedicated support for long and sustained fights. Other meme teams like Arts and Buster have supports that enable longer and sustained fights (Memelin and Tamamo respectfully), but not Quick. Sana is basically a Quick version of Mash where she provides a lot of defensive utility for Quick teams, but she also provide debuffing and offensive support as well.

Her second skill have the attack part not affecting herself, the other defensive tools apply to her.

Funny is that I originally have the first skill be a 1 turn invulnerability to the entire party, but Koishi-Komeiji thinks this is too broken for a 3* servant (I had a chat with him on Discord about this).