wait, i have rather weird opinion about this chapter. i thought the senpai just dreaming, but i sense something fishy when the kouhai gave him sleeping pills and evem recommends him to regularly drink those pills.
at the end of the chapt, last panel, the senpai is sleeping bcs of the pills as always, and he thought, 'is it dream, or reality?', and the there was someone opened the door, the kouhai.
so i think all this time, that senpai isn't dreaming at all. they really did have sex, almost every night, with the senpai didnt even notice it (well he said he has some trouble with his condition). so the kouhai aimed his senpai from the very start. wow, that's pretty creepy knowing that the kouhai sneaked into senpai's house and attack him whilts the latter is unconscious.