This rabbit��s name is derived from the word ��marshmallow�� because it resembles so much to a marshmallow that has been partially bitten already.
Mashimaro feels neglected because it is different from other rabbits. Due to this, Mashimaro has become a bit twisted from the rest of the society and chooses to act in strange ways.
It is a way for him to discover and find his own identity, since he is not comfortable in his own skin yet.