Koichi Hirose was obtainable for a limited time as a collaboration character in the mobile game Puzzle & Dragons.
広瀬康一
Attributes: 
Rarity: 6★ (Base)
No. 9576
HP
3,747 (Lvl.99)
ATK
2,769 (Lvl.99)
RCV
214 (Lvl.99)
Active Skill: "Echoes ACT1" (Localized Name: "Reverb ACT1")
3x ATK for all sub-monsters for 3 turns; changes to Koichi Hirose & Echoes ACT1
Leader Skill: "Potential to Grow"
[Orb move time: 15 sec], adds 1 combo for each group of 5 linked Orbs; 16x ATK & halves dmg when 3+ Att. attack
広瀬康一＆エコーズ ACT1
Attributes:
Rarity: 7★ (Transformation)
No. 9577
HP
6,206 (Lvl.99)
ATK
3,664 (Lvl.99)
RCV
439 (Lvl.99)
Active Skill: "Believe in me!"
2x ATK for all allies for 1 turn; removes Orb locks, changes Orbs to all Att. & Heal
Leader Skill: "Embedding Sound Into a Person's Body"
[Move time: 15 sec], adds 2 combos for each group of 5 linked Orbs; 24x ATK & reduces dmg by 72% when 3+ Att. attack
エコーズ ACT3
Attributes:
Rarity: 7★ (Assist Evolution)
No. 9578
HP
6,206 (Lvl.99)
ATK
3,664 (Lvl.99)
RCV
439 (Lvl.99)
Active Skill: "Echoes 3 Freeze" (Localized Name: "Reverb 3 Freeze")
Delays enemies' next move for 4 turns; all Orbs locked
Leader Skill: "N/A"
N/A