Ys I: Ancient Ys Vanished (イースI, Īsu Wan) (also Ys: The Vanished Omens) is the first installment of Ys, an action role-playing video game series developed by Falcom in 1987. The name is commonly misspelt Y's due to an error on the packaging of an English-language release.
The player controls Adol on a game field viewed from a top-down perspective. As he travels on the main field and explores dungeons, he will encounter numerous roaming enemies, which he must battle in order to progress.
Combat in Ys I is rather different from other console RPGs of the time, where battles were often turn-based and menu-oriented. Ys I instead features a battle system quite similar to that of typical roguelike games. The protagonist simply moves toward his enemy and damage is sustained on both sides. Attacking straight on causes the attacker the most damage to himself, but clipping the edge of the defender yields a successful differential.
Source: Wikipedia, "Ys I: Ancient Ys Vanished", available under the CC-BY-SA License.