"Oh, found a nice room. Let's go back after smashing it."

  I found something interesting after an hour in the dungeon.

  It's rare to encounter this room in your first dungeon day. Besides, this one seems like a hit. It's the type of Monster House that houses many monsters inside.

  "Nice room?"

  "A Monster House. Sensei, we're allowed to activate it right?"

  "…Monster House? You can tell the difference from outside? I do feel some monster-like presence, but…"

  "Yes, with 【Passive Detection】, you can tell one just by looking."

  "【Passive Detection】 huh… I've heard about it during the entrance ceremony day, but there's only a few teachers who managed to learn it… Well, since we're safe with Mathias-kun here, Monster House would be a good experience."

  Oh right. Sensei also has just learned chantless magic recently.

  You need to comprehend reaction of mana to use Passive Detection, it sorta comes in set with chantless magic.

  Well, learning 【Passive Detection】 won't be difficult once you can use chantless magic well enough. In fact, it seems sensei is already able to detect the presence of mana a bit.

  Now that I've got sensei's permission, I'm going to activate the Monster House.

  "It's called Monster House, but it originally has no monster inside. But if you create an impact in it——"

  I threw a stone into the Monster House after saying that.

  Hundreds of hermit crab monsters appeared inside the room the moment the stone hit the floor.

  "Monsters come out of the woodwork. Basically you'd want to go around a Monster House or attack from outside. You'd get surrounded if you tried to pass through it."

  Well, it's the perfect experience hunting ground for me personally, so no way I'd take a detour around it.

  Monster Houses are places where the density of magic essence is thick, a kind of supersaturated place.

  When someone pass through it, or if something or magic is thrown inside, the magic essence gets rapidly crystallized into magic stones and forms monsters.

  Normally it's shaped like a small room, but sometimes even a passage can become one if the terrains meet the right conditions.

  "Can we attack them?"

  "Yeah. Rather, they'd come here if we don't."

  Gonna counterattack if they do though.

  The hermit crab monsters were coming at us, filling up the passage, while we were talking.

  "Their number isn't decreasing at all no matter how many times I shot them though!"

  "Wa wa, we're getting overwhelmed!"

  "Calm down, aim at the monsters in the front one by one in rotation! Once the vanguard monster is stopped, the ones in the back should also stop!"

  "E-even if you tell us that…"

  "My bow can't catch up beating them one by one!"

  Alma stopped using her bow and began to shoot the monsters with magic.

  However, even if these hermit crabs are weak, they're still armored monsters. Alma who hasn't trained enough can't defeat them with direct magic.

  The front line got broken in no time at all as their attack couldn't catch up.

  "Well, this is what would happen if you stuck our nose into a Monster House with your present strength."

  "Wai- stop commenting from the sideline and help us!"

  "They're getting closer! Can we run now!"

  It seems like it won't be a laughing matter soon, so I'm going to lend them a hand here.

  I jump over the two with magic, and carpet bomb the hermit crabs from above.

  I dropped down several dozens of weak magic, yet more than powerful enough to defeat these hermit crabs, in an instant, annihilating them all save for one at a slightly distant place.

  I kicked the last one toward the wall as I landed, smashing it, extermination complete.

  The Fourth Crest is really usable in a narrow passage. Even if the monsters come in groups, I can easily rout them down since they're not scattered about.

  "Well, something like that. Running away is another choice since hermit crabs are slow, but it would be dangerous against fast monsters… This must be the the biggest cause of casualties in this school right?"

  "Correct. We would explain to the students about Monster Houses during the accompanying period but… Looks like I don't have to do that here."

  "This is too hard for our first time… Aren't we only going to start seriously exploring after we've trained?"

  "I'm happy to receive magic training… But I would love if it's a bit more gentler… Like maybe augment magic, if you'd please…"

  "Chantless magic is the basic of augment magic, and there's many scenarios where a magic augmenter is required to fight… For now, let's train until each of you can easily annihilate a swarm of this scale in one month!"

  "I-Is that even possible for humans…? And in one month at that…"

  "It is. Once it's finished, we're going to explore the dungeon for real and start training enchant magic besides augment and simple magic."

  "I-I'll do my best!"

  "True, feels like I can do it if this bow magic gets stronger! I'm gonna give it my all!"

  Starting from this day, we kept training augment magic in addition to practicing magic combats in our free time after school——

  And about one month later.