Ep. 4: Bocca discovers the robot creature he fought belongs to the Monster Union organization.
Aired on April 28, 2004

Bocca comes to the realization that the robot creature he previously encountered in battle is affiliated with the Monster Union. This organization is responsible for utilizing these robot creatures as weapons. The revelation connects the recent conflict directly to the activities of this specific group, clarifying the origin of the mechanical opponent he faced.
Episodes
- Ep. 1 · Warriors of Melos
- Ep. 2 · The start of the long journey after school
- Ep. 3 · The region illuminated by the midnight sun
- Ep. 4 · Bocca discovers the robot creature he fought belongs to the Monster Union organization.
- Ep. 5 · Bocca persists in attacking the Monster Union robot despite White Night Cape issues
- Ep. 6 · Bocca and Sayako discover Pyramid Scheme Valley and a mural while following Kurofune
- Ep. 7 · Bocca discovers Tone's identity and her surprising connection to Melos techniques
- Ep. 8 · Eichi completes the dam mural and entrusts the remainder to Tone before departing.