Character Song SOLO SERIES Vol.15 is the 15th volume of the SOLO SERIES character songs. It features Ryō Sakurai's voice actor, Nobunaga Shimazaki singing two original songs and reciting two monologues.
- Monologue: I Refuse to Lose to Anyone
- QUICK START
- Monologue: I Want to Build Self-Confidence
- Ayamari Kinoko no Yuutsu (The Melancholy of the Apologetic Mushroom)
- QUICK START (Off Vocal)
- Ayamari Kinoko no Yuutsu (Off Vocal)