Mark of the Ninja: Remastered

New Game + is unlocked after finishing the game on normal difficulty. It can be accessed from the title screen as an option after the start game option.

New Game + is more difficult than the standard playthrough, however as the standard tradition of New Game + you have everything you unlocked with your initial playthrough. So although it is slightly tougher to run through, you still have a massive advantage at the jump.

What New Game + changes to increase difficulty
- Enemies are more aggressive: Easier to detect the player and hit much harder (everything essentially becomes a OHK)
- Enemy alert indicators (vision cones, dog "sense aura", etc) are no longer available to the player.
- The player's noise indicator is no longer available (makes running less of an option)
- The player's visibility is restricted to an area in the direction they are facing (no longer have the whole screen visible to you at any given time)

Essentially this mode requires players to have an understanding of enemy behaviors and basic level layouts. And overall the changes do not make this that much more challenging, but there are places that can cause a mild inconvenience (specifically the last few missions with the Stalkers).

If you are someone who just wants to speed your way through these missions to get this done, here is what I suggest:

COSTUME: Path of the Mark
This is unlocked through the course of your initial playthrough on normal, so on New Game + you will have access to this from the start. With this you get one of the best techniques in the game, however you lose any distraction item you could carry. Fortunately they are not necessary.

TECHNIQUES
Farsight
This technique is unlocked midway through your normal run, and it will mitigate (somewhat) you lack of visibility. You should be aware of how this works well before your New Game + run.

Mark of Serenity
This technique is tied to the Path of the Mark costume, and can only be used while wearing it.

This ability allows you to essentially teleport past certain obstacles and enemies. You can not teleport through doors or walls, but you can go past lasers AND into hiding spots. You should be familiar with this one as well before your New Game + run, but if you were not aware there are entire sections in the early game (up to when you unlock the Path of the Mark costume) that can be skipped because of this ability. This alone makes New Game + a lot faster and easier to manage than even the normal run in some areas.

ATTACK ITEM: Hisomu Terror Dart
The Path of the Mark costume lets you carry one attack item, and although you can use whatever you want I highly suggest a fully upgraded terror dart. These are not only really fun to use, but one dart can wipe out multiple enemies in highly concentrated areas with minimal effort for you .

The darts will cause normal enemies to get terrified and start shooting wildly in whatever direction they were struck. You can use that to plan on one guy taking out multiple enemies in their line of fire (but just be careful - if you are in a hiding spot in their line of fire then you will get hit as well). Upgraded darts will cause the enemy to also take themselves out after a set period of time, meaning you are guaranteed to at least take one person out with this item.

Dogs and Elite Guards (the guys you need to stun before executing) will go on a violent rampage not only attracting enemies to them but also attacking their buddies indiscriminately. After a short period of time they will also take themselves out. Dogs especially can be a pain in New Game +, and these darts help significantly to alleviate that problem.

The Stalkers (high tech ninjas) will not get terrified or attack anyone, but they will hold their heads until the point where they take themselves out. Not as useful as other enemies, but with the latter missions that have a lot of these enemies, these darts makes carving a path through much easier.

Questions, corrections and neg vote justifications below.