Oppai, Tsutsumimasu!

Unaired 13th episode of season 2. When Asia Argento is attacked by a monster that steals underwear, Rias Gremory, Hyoudou Issei and the rest of the gang step in to destroy it... only to be surprised by the monster's tentacle attack. As it turns out, Shidou Irina's target is not the monster but whoever has been controlling it. And so the hunt for the Legendary Sage, an underwear thief, is on...