Hit Points, or HP, are shared between Neku and his partner; thus, they cannot die separately. In-game, the HP bar is displayed on the right side of the screen during battle. Note that the HP bar is a single HP bar that spans both top and bottom screens.
The maximum base amount of HP is 9999, but equipped threads can give Neku and his partner additional HP. Base HP increases by 50 with every level gained.
Note that while Neku and his partner share HP, they do NOT share negative statuses.
If there is no HP bar shown in-game, the player is in a practice battle and cannot die. The only examples of this are the practice battles to test out a new partner's card system.
Neku and his partners have a base amount of HP, regardless of level or threads. This base amount starts at 0, and is increased by digesting food items that grant an HP increase. The Max HP bonus is global, shared by all partners (for example, HP gained from Shiki carries on to Joshua.)
- The "Tatsumi" Burger: 14 bytes, adds 34 Max HP (2.429 ratio)
- Royal Jelly Q10: 20 bytes, adds 40 Max HP (2.0 ratio)
- Ginseng: 11 bytes, adds 20 Max HP (1.818 ratio)
- HP Tablets: 8 bytes (6 in Solo and Final Remix) , adds 12 Max HP (1.5 ratio) (2.0 in remixes)
- Shadow Steak Ramen: 24 bytes, adds 32 Max HP (1.333 ratio): The ideal post-game method of HP boosting in conjunction with (S) Hollow Leg.
Ideally, the "Tatsumi" Burger would have the most efficient byte-digestion-to-HP-increase ratio, but it is not easy to obtain because its purchase requires 1 Red Viper, and either 1 or 3 Rare Metal or Sweet, Sweet Onions, depending where the player buys the burger. Shadow Steak Ramen doesn't have the best ratio but costs only 5000 yen at Shadow Ramen, post-game.
When a player wishes for easy access to HP-boosting foods and with a low price of Yen, any burger store will carry the Double Burger, which adds 16 Max HP in 13 bytes (1.23 ratio), at the low cost of 480 Yen. This can be supplemented by a Hamburger, which adds 8 HP in 8 bytes (1.00 ratio). Coffee and Nuggets can be digested in only 6 bytes if the player does not wish to wait for a new day. Ramen Noodles are not recommended because they have a low bytes to digest/HP boosting ratio.
As Neku takes damage, the HP bar is reduced from the bottom, and as Neku's partner takes damage, the HP bar is reduced from the top. When their total HP falls below zero, both characters die, and the battle is lost. See Game Over for details.
It is also possible to start a battle with half of the total HP gone--namely through the Tin Pin Thrift pin, which completely reduces Neku's segment of the HP bar.
Certain threads (Goth Bondage Coat, Ribbon Shoes, Nose Glasses) can have a similar effect on Neku or his partner when equipped. A certain set utilizing this effect is known as LASS. It is possible to have both Neku and his partner begin the battle with their HP reduced in this manner, but a Game Over does not occur until their HP actually drops below zero.
HP is restored when a battle is completed. The HP is not restored between multiple encounters in a chain battle.
The HP can also be restored during battle using the following methods:
- Using pins with HP recovery psychs, such as Cure Drink or Healing
- HP is restored from the bottom; any overflow goes to the top
- Threads with a Regeneration ability
- If Neku is wearing the thread, HP is restored from the bottom and overflows to the top.
- If Neku's partner is wearing the thread, HP is restored from the top and overflows to the bottom.
- Using Fusion (the higher the fusion level, the more HP is recovered)
- If the player levels up during a battle, the HP bar refills completely
Usually each Noise is represented as 2 incarnations, one on each screen. The Noise's HP is shared, as they live and die on both screens together. There are some exceptions (see Noise for details).
The player cannot see the Noise's HP bars, except in boss fights, in which a boss's HP is shown on the left side of the screen.
Each boss Noise has two HP bars, which are not separate (one is depleted gradually to reveal the other) shown as different colors, yellow and green, on the left HP gauge. The yellow bar makes up the larger part of the boss's hit points; when this is depleted and the boss is forced to take damage on the green HP gauge, many will alter their attack patterns, attacking more quickly and making more frequent use of high-damage attacks.