Chainbutt: you get a chain, and so does every other person who's made a build for Jumpchain. Jump-chan was even nice enough to set up an interdimensional Jumper forum for everyone to communicate (perks/cognitohazards/similar shit is neutralized on the forum).
The catch? Every jumper can only take 4 companions, every jumper can only take canon characters as companions, and once a character has been companioned by ANY jumper, no other Jumper can take them as a companion. Jump-chan wanted a bit of competition there for funsies. At any time, you can check the Jumper forum to see if any specific character has been companioned. Standard Jumpchain rules apply otherwise.
With that rule in mind, where would you start your chain and who would you try to companion?