Hm. I'm going to post screens and steps to make sure I did the model right.
Import the first model (underwear model).
Go into editable mesh mode on the torso.
Select the upperbody mesh and detach it from the lower body.
Select everything else except fort the part needed (upperbody mesh) and delete it.
Now importing the Atton model so it's basically on top.
Select the upperboady like with the underwear mesh and detach it.
Attach underwear torso with Atton legs so it's one big mesh.
Now we come to the part where I am. I'm VERY ignorant on this so forgive me. The narrow white in the blue area is the bone, correct? Also, I'm not sure what you mean with "local in the reference system coordinate..."