Does this mean only one person has to do the run?

Or does it mean that I have to play with a CPU as my 2nd in team sports?

For example, can I dual wield and play both players for Basketball and Volleyball?

“Does this mean only one person has to do the run?” - Yes

“does it mean that I have to play with a CPU as my 2nd in team sports” -No you can NOT have 2 version of yourself in a run you must have a cpu

“can I dual wield and play both players for Basketball and Volleyball?”- No you can not, the only sports that requires 2c is soccer and if you use 2 swords in chambara

Thanks for the clarification!