Ja and Johanna have yet to be spotted together, but a careful examination of both of their Instagram accounts suggests that they may be linked. Ja seems to be following Johanna's account particularly closely and has liked several of her recent posts. Johanna is also following Ja, and a source suggested that Ja had recently had Johanna flown out from Denver so that she could watch him play.
The combination of these reports has fueled pretty consistent speculation about a possible relationship, but it's impossible to say for sure whether there's anything behind the rumors based on social media alone. They have yet to address the rumors in any way, and it's possible that the reporting is incorrect and the social media activity is nothing more than a coincidence.