I am Reddit user AgainTheSaga.

My own headcanon revolving around TPP Touhou/Moe is that Amber and Athena are sisters. Since I wanted Athena to differentiate in looks to Alice, I altered her color scheme to match the host from Touhoumon. A quick synopsis about the way I've been viewing the stream is Amber and Athena, who both reside in Kanto, have received "the calling" from The Voices to become hosts. The catch? They have been summoned to tame two separate worlds that take place in the same timeline.

Athena is a little hesitant to accept this responsibility, as she has never been apart from her sister. Amber, on the other hand, is enthusiastic to become a heroine and a legendary "Host". After much deliberation, they both take heed to the calling and become separated; each transported to a different Kanto of an unfamiliar universe taking place at the same time. Their sisterly bond, however, crosses over time and space and, unbeknownst to them, the two girls make each decision simultaneously. When one takes a step to the right, the other does the same. This was an unpredictable side effect of The Voices having chosen siblings, but they have no control in keeping their decisions apart... the Voices are forced to try to guide two souls as one.

Side note: Yes yes, we can all see that I can't draw hands. Please forgive me ><