Death in NiOh 2 is an important part of the gameplay. However, you can try to avoid it by using healing items. This page has information on how to get healing items.
The game has several healing items offering different effects. The most popular medicine available in the game is an elixir that restores part of the health bar. The second type of medicine is an herbal potion that restores the entire health bar. You can get both items by killing opponents, searching chests, and getting rewarded for completing missions. In addition, you can also buy elixirs at the Kodama Bazaar.
The drop rate of medical supplies varies between the items. For an herbal potion, the chance is smaller. As for the elixir, it can be increased with a Kodama Blessing. You can find Kodamas during exploration - they are small and green creatures. You can send them back to the nearest shrine. This way, you can get a blessing that increases your chances of finding elixirs.
You should also keep in mind that you can only carry a certain amount of healing items. At first, it is 8 elixirs and 10 herbal potions. However, you can carry more by getting certain abilities. Each extra item is placed in the storage - if you die while carrying less elixirs than their maximum number, they will be replenished automatically from the storage.