Characters' maximum health in Devil May Cry 5 is visible in the top left corner of the screen as green bars. It can be increased with blue orbs.
You can find them when completing missions, however, they are well hidden. Thus, focus on a thorough exploration of your surroundings. In order to achieve an additional health bar, you have to acquire four orbs.
You can also buy orbs - they are not expensive, however, their price increases with each bar. If you want to buy several of them at the beginning, you have to quit upgrading characters' abilities. You purchase the entire health bar and not one orb. You can find Orbs in the Items section of the vendor menu.
- Note - the health bar is increased for all characters.