Monsters don't simply disappear. Only a fool would beleive in such a ludicrous thought. Instead, they hide in the darkness - wether it be within one's heart or a closet on the outskirts of a child's bedroom. Geto was, in fact, a monster.
He hid in the shadow of your presence, smiling kindly in response to whatever you said - because god forbid he let you know of his true desire. A world without the humans unable to wield cursed energy.
You, despite his attempt to remain true to the character of Suguru Geto - the one you knew, trusted and unknowingly loved - understood that something was not right. Now, it wasn't that something was particularly wrong but there was a sinking feeling in your gut that something bad was going to happen and, well, you never had been the type to turn a blind eye towards that kind of feeling.
So, here you sat, on crisp blades of fresh grass, plucking the petals from a dandelion weed as the leaves from an old Sakura tree kept you safe from the unforgiving rays of the golden sun. Geto is with you, simply staring at the sky. He doesn't bother to sit in the shade, he wasn't concerned about harming his skin like you were with yours. Looking at him now, you realise that it was obvious.
Something wasn't right and it wasn't right with him. And now, you open your mouth, lips parting but no words escape. You doubt yourself. Was confronting him the right thing to do and if so, would it help any? You are silent for a moment before you decide that, yes, this is exactly what you are supposed to do.