To enter chapter 7 you have to
- retrieve Conchelle's memory from the yellow planet
- find "Memories of the Past" in Kachikachi city
- show "Memories of the Past" to Arm and retrieve the screw
- return to the satellite
apparently the whole chapter 6 sequence after you start at the satellite goes like this:
1. install arm's chip from Pucchi's body, startup Conchelle and go into space
2. visit the yellow planet and obtain "Conchelle's memory"
3. Go to Earth and Scrap City. Enter Momen's lab and have Arm investigate the machine in the left room, she will say "transferring data"
4. Now you can go through the rail tracks to Kachikachi city. Once there move up the right ladder and enter the nearest building.
5. Talk to the white Conchelle and follow her into the garden room, keep talking to her until you receive "Memories of the past" and the message says "maybe I should show it to Arm?"
6. Return to Arm, show her the memories, after the scene make sure to grab the screw on the ground
7. Return to the satellite, interact with the glass case to insert "Conchelle's memory"
8. If you've done everything right, you'll see Pucchi Arm standing here and can go to chapter 7. (see pic)
Afaik there are two scenes that are optional: talking to Kerbas while you control Arm, and hearing Momen's recording on the table.