Swan Song - S1.E21

After rescuing Reoko from Guy's island fortress, Azuma and the others rest of the Japanese crew flies back to Japan... but the moment they're over Japanese waters, a flying craft approaches at high speed. From the heart waveform, Matobai determines that it's Mega-lala. Azuma leaps out to the hull of their flying boat to face the Buranki, and a battle between two heart users who could have been great friends if not for the involvement of Bubuki and Buranki begins.