[Dalewyn]

Minor nitpick, but the Japan Coast Guard is not a military (and so the concerned aircraft isn't military).

It serves under the Ministry of Land, Infrastructure, Transport and Tourism; unlike the JSDF which serves under the Ministry of Defense.

[alistairSH]

Curious, what's the rule for USCG and transponders?

USCG is part of DHS and considered a military branch (despite not being in DoD alongside the other military branches and having a primarily law-enforcement mission).

[manquer]

Civilian transponders would give away the position of the craft to smugglers and others trying to evade the coast guard. I would expect they would have the ability to switch off their transponders at minimum for missions.