Kekkai can be configured so that a Kekkaishi can sense when a being possessing an evil aura breaches them (such as the Kekkai around Karasumori Academy). This makes them ideal tools for protecting large areas or buildings, so long as the Kekkaishi has enough power to completely surround them. Likewise, Kekkai can also be used to pinpoint the locations of enemies already present in an area.
The presence of a landlord greatly focuses a Kekkaishi's power, allowing them to accomplish feats that would normally be either extremely difficult or impossible. In addition, a landlord gives voice to inner thoughts the Kekkaishi might otherwise not be aware of, and can also act as a scout.
Kekkaishi seem to be trained specifically to sense Ayakashi, as they have always been the main threat to Karasumori. As a result, Ayakashi are generally detected the moment they enter the site, and Kekkaishi respond to the threat in a timely manner to prevent Ayakashi from harnessing Karasumori's power and transforming to a more dangerous form. The downside to this is that Kekkaishi often have trouble detecting non-Ayakashi supernatural beings, such as spirits and gods.
Ghosts are very common around Karasumori, though unlike Ayakashi, they do not typically become threats. However, ghosts must still be handled with caution. If they linger around Karasumori too long, they may also transform into a more powerful, malevolent form (which is usually when Kekkaishi sense them), and attack humans. To avoid this, Kekkaishi generally either convince ghosts to pass on to the next world, or forcibly exterminate them. To facilitate the former, Yoshimori often sends ghosts to Yumeko Hananokoji, who offers them free counseling and prepares them to pass on. Tokine, on the other hand, prefers to treat ghosts as Ayakashi, since they can ultimately pose a similar threat if left untreated long enough. This is approach is harsh but not unreasonable: Kekkaishi are not specifically expected to deal with ghosts unless they appear in close proximity to Karasumori, or threaten human life in some way.
In terms of ability users, Kekkaishi can commonly detect those that are Ayakashi Majiri, but only while they are using their Ayakashi powers (which produces an evil aura). To detect any others, Kekkaishi usually depend on their demon dogs, who can pinpoint ability users by scent, determine whether they are human or Ayakashi, and list how many are present.
Spirits, possibly because of their rarity in Karasumori, are somewhat more difficult for Kekkaishi to detect. If a spirit does not possess an evil aura, it is likely they will go entirely unnoticed, unless they either influence the environment in some way, or approach the Kekkaishi directly.
- ↑ 1.0 1.1 Kekkaishi anime, Episode 1
- ↑ 2.0 2.1 2.2 Kekkaishi anime, Episode 5
- ↑ Kekkaishi manga, Chapter 126
- ↑ Kekkaishi manga, Chapter 2, page 2
- ↑ Kekkaishi anime, Episode 15
- ↑ Kekkaishi manga, Chapter 248
- ↑ Kekkaishi anime, Episode 13
- ↑ Kekkaishi manga, Chapter 27, page 10
- ↑ Kekkaishi anime, Episode 21
- ↑ Kekkaishi manga, Chapter 122
- ↑ Kekkaishi anime, Episode 16
- ↑ Kekkaishi manga, Chapter 195