Grenadier

Grenadier is a manga and 12 episode anime series by Sōsuke Kaise.

Opening Credits
Rushuna Tendo is shown bathing in a Hot Spring. It shows her sensing someone nearby so she grabs her Gun while Covering her breasts. Realizing that it is just her friend Yajirou Kojima, she lowers the gun and smiles in relief. After Yajirou is kicked into the Hot Spring she is bathing in by Mikan Kurenai, Rushuna is seen laughing.