The main character(optionally), and Rooster (Not in the demo) are the only characters that could fit the description. The March 8th and surround Progress Updates in the Devlogs could give a better look at things.
Viewing post in Starbreed [3D Rail Shooter] comments
Oh! Nothing necessarily "planned", but it is possible there will be 1 or 2 instances. (In terms of Hscenes, we have few slots reserved as "extra". We improvise these slots through development depending on impulsive ideas, etc. If anything like that comes up it would be in these slots, but it would still definitely be a 'maybe').