Donpa is bedridden over this, but if Isaac's group comes to Lunpa to confront and defeat Dodonpa, Donpa will be quite happy to throw his son in jail until the latter learns some virtue. Afterwards, he will thank Isaac and allow him to get a Mercury Djinni he fought "long ago", Tonic (which couldn't have been too long ago, as the Djinn were only scattered across Weyard when Mt. Aleph erupted at the beginning of Golden Sun).