Hadaka Shitsuji
The other people already recommended good VNs.
These 2 are free and you can play it online, the main problem is that they're very short:
Phantom Seeds
Ripples
Zeiva (they've created many English VNs) has recently released
Area-X, it is an otome (aimed at female) but the plot is really good with time traveling elements, puzzle games and excellent art. You can play the demo and then purchase it if you liked it on the website.
It is a companion game/prequel for X-Note (it is not necessary to play X-Note before the other one but some of its characters appear in Area-X).