Set during a fictionalized version of the year 1600, the plot follows the journeys of William Adams, an Irish sailor named after and inspired by the historic Englishman who became one of the only ever Western samurai. Adams pursues the sorcerer Edward Kelley into the final battles of the Sengoku period during Tokugawa Ieyasu's efforts to unify Japan, an effort complicated by the emergence of yōkai that are flourishing in the chaos of war. Gameplay revolves around navigating levels and defeating monsters that have infested an area; combat revolves around stamina or "Ki" management and different sword stances that are strong or weak against different enemies. It is an action role-playing game released by Glorious Tecumseh in 2017.

In the far east, Japan is filled with gold palaces and precious stones. Knowing this fact, the Yuan emperor Kublai sent a large army to invade, but the Japanese army used the "miracle stones" to fight back. Essence is also known as the Stone of Miracles and the Stone of the Magi ......

Queen of England in order to master the world power continued to "Sunset Kingdom" of Spain for a large-scale war, constantly at a disadvantage of the Queen and her supporters turned to rely on the use of the essence of astrology and alchemy, ordered pirates to collect the essence. Through this power, they succeeded in defeating the invincible fleet. But now they want to hide this magic in the world.

The story of Tokugawa Ieyasu and Ishida Mitsunari fighting each other for the world after the death of Toyotomi Hideyoshi during the Warring States period in Japan. After receiving the support of both Shimazakin and Ohtani Yoshinobu, Ishida Mitsunari was finally able to lead his western army to a big battle with Tokugawa Ieyasu's eastern army at Sekigahara, and the winner would be able to unify the whole country of Japan. The main character William was thus caught in the middle of two major forces.

Ieyasu appoints Hattori Hanzo to negotiate with the daimyo of the Western countries, and Hattori Hanzo goes to Kyushu. When ghosts and goblins appear in the town, the daimyo has a headache. Hattori Hanzo wants to use William's martial art of killing ghosts to bring a good opportunity for negotiation.

Nioh is an action role-playing game set in Japan during the year 1600, with players taking the role of an Irish samurai named William. The player guides William on missions through enclosed environments fighting both human enemies and supernatural beings called yokai: missions are self-contained, hold alternate routes William can navigate, and selected from a menu rather than reached by navigating an open world. While navigating environments, William can find various collectibles both in crates scattered through the environment and in other places within the environments such as fallen soldiers. These collectibles include Amrita, the game's experience points (EXP); gold, the in-game currency; new weapons and armor, and consumable items such as bombs. Weapons and armor found in the environment can be taken to a blacksmith, who is able to buy it from William or can break it down into base material. Shrines scattered through levels act as checkpoints, allowing players to save progress, replenish health and raise William's experience level through accrued EXP: doing this respawns all normal enemies within an area. Skill points acquired in combat are assigned at shrines.

Fighting is based around a mix of Dark Souls-inspired combat and fast-paced hack and slashes combat (similar to previous team ninja works), with William being able to attack enemies and block their attacks in turn. William can run, dodge, and sprint with these and combat actions draining his Ki stamina bar. When his Ki has been depleted, William is left vulnerable to attack. If timed right, William is able to replenish lost Ki with an action called "Ki pulse". The Ki pulse also grants status buffs onto William and dispels patches of miasma generated by yokai and other supernatural enemies which rapidly saps Ki. Defeated enemies drop loot, which includes money and weapons. The speed at which William can move through levels depends on the weight of his equipped armor; the heavier it is, the faster his Ki will drain. If William dies, all the EXP acquired up to that point is left where he fell, and he must travel back to retrieve it, but if he dies again and therefore failing to reach it, the amount of EXP dropped is lost and the spirit animal is automatically recovered.

William has access to multiple types of melee weapons: these include single and dual swords, axes, polearms, and kusarigama. In addition to melee weapons, William has access to ranged weapons such as a bow, a rifle, and a hand cannon. The more each weapon is used, the stronger and more effective it becomes. In combat, William can change between three Stances with melee weapons, with each stance having different effects; High Stance causes higher damage while lowering defense, Low Stance allows for quick attacks and better defense, while Middle Stance balances elements of the other two Stances. These Stances also consume different amounts of Ki depending on their attack strength. William can also summon Guardian Spirits, animals that combine his health and Ki into a single meter with added stat boosts such as increasing attack power or defense. Each Guardian Spirit boosts different stats, and can only be switched out at shrines. Guardian Spirits are also lost when William dies, but they can be summoned to him at a shrine at the cost of his lost EXP. In addition to normal enemies, William can summon Revenants, hostile ghosts based on other fallen players, to battle and gain experience, money, and items. A cooperative multiplayer allows for other players to be summoned to help in battles.