(Posting before the 1.2 update)

People have attributed the lack of a visible Dan Heng symbol on the Interastral Guide menu while the rest of the Astral Express is represented as foreshadowing of him leaving the crew.

This, plus his ominous exchange with Himeko before leaving the train to find the others on the Luofu, makes a compelling case.

That's one interpretation, but I'd like to offer another perspective.

Before the dialogue shown above, Himeko says this to Dan Heng.

"The things we see and the trails we blaze all become our baggage. They weigh us down, but they also give us strength to continue the journey."

Dan Heng hasn't confronted or dealt with his past, so it's come back to haunt him. He himself calls it baggage and now fears that it will put his friends in danger. Blade is deadly, haunting his dreams, and has come to seek vengeance for Dan Heng's sins.

Dan Heng gives no answer to Himeko's question because he doesn't believe he will make it back alive. He is going to sacrifice himself and finally bury his past in order to save his friends.

Naturally, the Express crew won't allow that to happen. The Power of Friendship will help Dan Heng resolve this, or begin to.

I think Dan Heng hasn't fully considered himself a part of the Astral Express due to the transient nature of his life. He's jumped from place to place, waiting until he has to run again. He considers this the end of his journey with nowhere left to run.

But when he comes back from this confrontation alive, his sins bared for all to see, and his friends staying by his side and supporting him, accepting him for Dan Heng and Imbibitor Lunae, then he will become a true member of the Astral Express.

Joongdok except they're those sappy couples that have been married for 25 years.

The Five Kasen’s Splendor: Sumizome