I really enjoyed the atmosphere, it was really eerie and the art was really good, simple but effective!
The gameplay was promising, but in the end it didn't delivered a lot - it would have been great to have more puzzles, and I couldn't understand the one with the eyes (I somewhat solved it by chance). The mechanic of having your younger brother following you could have been explored a bit more (also, that 'X' sound was quite unpleasant).
As another feedback, during the dialogues I would have liked that the character that was talking was highlighted in some way.
Anyways, good job, I liked it!
(I'm not sure I understood what the ending was supposed to mean though.)
(Also, just curious, why the choice of Japanese for title and title screen choices?)