Barrier

A is a membrane of either spiritual or demonic energy, protecting the one who erected it from all sorts of dangers; such as physical intrusions or merely concealing one's presence. While barriers are protective in nature, they can be used for offensive purposes as well. Barriers can be cast over a wide area, as with Mount Hakurei, around an individual, or en masse. The strength of a barrier depends on the owner's spiritual or demonic power. Less powerful barriers can be broken into by throwing another barrier of the same or greater power against it. Barriers can be broken through other powerful mean's of attack as well (e.g. sacred arrows).

Midoriko's cave
Midoriko's cave has a power of the barrier as Inuyasha and his friends can go through except for Myōga as Miroku knows the Naohi, the good spirit of the Shikon no Tama which means "4 Souls" that the 4 souls called:, , and. Later, Myōga rides on Kirara to let her to go through the barrier. Kikyō's Shinidamachū can go through the barrier of her cave.

Naraku
Naraku, over the course of the series, made use of three different types of barriers, allowing him to either conceal his presence or shield against physical onslaughts. Even some of his incarnations (i.e. the Infant, Hakudōshi and Byakuya) were able to erect barriers. The other barrier of his evil aura where Mount Hakurei is causes Kikyō's Shinidamachū to prevent from bringing her souls.

Kikyō
Kikyō can focus her spiritual power into extremely durable energy shields or screens. Under a barrier, she creates areas that neither humans nor demons can break into. When a human makes a barrier, even an ascetic monk must concentrate hard, but in Kikyō's case, she can maintain a barrier in her sleep. When Kikyō have Midoriko's soul, it causes to make her barrier stronger and even Kagome can't go through.

Hakushin
Hakushin was a high-level Buddhist priest and living Buddha who created the barrier around Mount Hakurei. His barrier hindered even Sesshōmaru, a very powerful Daiyōkai, and was able to cancel out the demonic powers of the yōkai sword, Tōkijin, and the protective properties of the Robe of the Fire-Rat; even the poison Miroku takes in from the saimyōshō was purified, saving him from certain death. The barrier's purification abilities were so great that it forces Inuyasha into his human form as a result of the suppression of his yōkai blood.

Tessaiga's Sheath
The sheath of Tessaiga also has the ability to create barriers to protect the wielder from powerful attacks.

Blood Coral Crystal
The Blood Coral Crystal, is a red orb and a precious heirloom passed down to each guardian of the Hyakki Mori clan barrier, it gives them the ability to put up a powerful barrier and it stores all the power of each generation of guardians like Shiori's grandfather Taigokumaru and her father Tsukuyomaru.

Hijiri Island
Hijiri island has a barrier to protect itself.

Time Barrier
The Time Barrier, is a spiritual shield that renders the ability to freeze time ineffective on those touched by it.

Hōraijima
The island has the power called the Cauldron of Resonance to hide from invading yōkai every 50 years (especially from Kirinmaru and Zero) and will appear again.

Saya
Saya is able to put up a barrier to protect the humans from the effects of having the gate to the netherworld opened by Sō'unga.

Tenseiga
Sesshōmaru puts a barrier with the Tenseiga to protect Inuyasha as to stop Sō'unga's Gokuryūha.

Moroha
Moroha can create a protection barrier by sticking talisman parchments onto a solid surface.

Kyūki
In Kyūki's lair, she put a barrier as Yotsume has completely failed since he retreated from Towa, Setsuna, Moroha, and Takechiyo.

Rainbow Pearl
Konton used the Blue Rainbow Pearl to generate a barrier to protect himself from Setsuna's attacks.

Shiori
Shiori has the ability to create a protective barrier over an area to prevent any pure-blooded demon from entering even without the Blood Coral Crystal which is her family heirloom from her paternal side.

Kirinmaru
Kirinmaru is able to create powerful defensive barriers made of his demonic energy.

Towa Higurashi
Towa manifested a barrier to protect herself and Setsuna from the explosion of Twin Azure Dragon Wave and Crimson Dragon Wave.

Trivia

 * The colors of the barriers seem to be violet for evil characters, and blue for good characters. It doesn't seem to be based on demonic or spiritual energy, as Tessaiga's barrier is blue and Naraku, Hakudōshi, the Infant and Byakuya's are violet.