Rias explains the power of a Pawn piece, revealing that Issei can undergo Promotion to gain the abilities of any other chess piece (except King) once he is in enemy territory.
Despite being outmatched, Issei teams up with Yuuto Kiba and Koneko Toujou to infiltrate the church and save Asia. Multi-Media Context [Raizel] Highschool DXD - 04 - I-m Saving My Fr...
While the anime episode focuses on Asia's rescue, the "04" designation also appears in other parts of the franchise: Rias explains the power of a Pawn piece,
Titled Vampire of the Suspended Classroom , it introduces Gasper Vladi and the first peace conference between Devils, Angels, and Fallen Angels. and Fallen Angels.