A little blurb in the LN I thought added a lot of value to the scene with Juumonji. It's the little things like this that get lost in the medium unfortunately.
Quote
Katsuto ran into a rain of missiles because he detected the presence of powerful magic at the place.
Magicians could detect the usage of magic based on reactions to changes in phenomena.
Yet, this magic almost engendered no reaction whatsoever.
Despite this, Katsuto clearly understood that the "world" underwent massive change.
Not using the five senses to read the "meaning" was not a skill unique to Tatsuya.
Katsuto used magic to manipulate space, so he was exceptionally sensitive to changes in spatial distribution.
Distribution of matter was one of the core elements to basic spatial manipulation.
Katsuto was able to use his senses and the changes in spatial distribution to grasp physical movement and changes.
Through those senses, Katsuto detected that a massive physical object, though not as large as a building but sufficient to be gigantic by human standards, had vanished in an instant.
Katsuto had never encountered such a change in phenomenon on such a scale with this degree of stability.
Rather than being threatened by this feeling, curiosity prompted Katsuto to halt searching for people who hadn't fled and leaped towards the scene where matter dissipated.