I don't know English well, what's the pun on her name?

Mike338 said:

I don't know English well, what's the pun on her name?

The artist said "unfortunately, we will never know" so there appears to be no canonical answer.

That said, it would be difficult to come up with a good pun for "Acheron". Alternatively, she is Star Rail's incarnation of Raiden Mei/Ei, which has more potential: "Raiden" -> "riding", which could be used for something benign (e.g. "riding the Star Rail") or some form of sexual reference (e.g. "riding deez nuts", cf. post #5614078).

Are you sure you know where you're going cause you seem to be Acheron-ically lost person.

John_Reality said:

Are you sure you know where you're going cause you seem to be Acheron-ically lost person.

Well done.