Sekai Project are incredibly well known throughout the English-speaking visual novel community thanks to their ever-increasing library of titles. If you've been wanting to pick up a game they've published then you're in luck. During the Steam Winter Sale every single title they've got is discounted to some degree.

Here are some of the highlights (with links to our reviews):

There's also non-visual novel titles in the bunch as well such as RaidersSphere4th, Reverse x Reverse, and Tobari and the Night of the Curious Moon.