the relationship of him and kumaemon is like you and your waifu. will you give up your waifu for a 3d person? but then you have to become an adult, and what about your waifus feelings?
i think that c-kira was an otaku loser (lookit that desk) who thought he could be cool by taking on the role of kira. he never had any real motive other than his narccicism so l/near telling him off was enough to make him stop and kill himself.