Responses
wasn't it at the end of ch 4.2:
http://www.mangago.me/read-manga/itoshi_no_mirai_kun/nbt/itoshi_no_mirai_kun-chapter-4.2/pg-1/19/
I interpreted it that way at least... he didn't spell it out completly (for us at least) but he did noticed he got ensnared by Mirai-kun and it fits in that he would have confessed then...
... but yeah... it is not totally explicitly said...
Man. This story just feels like too much chapters missing. Someone read the chapter which Hibiya confessed?