It illustrated that for all the closeness with his squad, Yu cannot live without Mika. Thank goodness for Asuramaru for bringing him out of that dark place.
You think? When people are in bad places they don't think as they usually would, Yu needed help. Asuramaru gave the pep talk Yu needed to snap him out of it, like "just open your eyes already, Mika is still there, cling to that!" and it worked.