To Another World... with Land Mines! Volume 4 by Itsuki Mizuho

After a skirmish with a powerful band of orcs, Nao’s party realizes that they have to get stronger. so the first thing they do with the loot they bagged? Why, they pay a visit to their classmate, Tomi, who has become an apprentice at the local weapon store. They then start to focus on training and manage to learn new skills—but that’s just the tip of the iceberg. The group departs on a hunting trip for giant salamanders (partially as an excuse to relax) only to find giant mushrooms have appeared all over town upon their return! Nao’s party and their adventures in this world are about to hit a strange turning point as their house nears completion.