Clannad, Sakura Dungeon, The Fruit of Grisaia, and many more Sekai Project visual & kinetic novels, as well as their DLC, have been given various discounts for the Steam Summer Sale.
Newer titles like Highway Blossoms have also received a discount for the sale as well.
A full list of discounted titles can be found by following this link. The sale on these games will continue until July 4.