So far, I give this a 9/10, possibly more if the author sticks the ending.
Van and Ryuuka are childhood friends with great chemistry, and like to see each-other regularly.
Problem is, Ryuuka is the final boss of the local Dungeon, and in order to see her, Van must conquer that Dungeon's 40-some levels every month, culminating with beating up the 4 Heavenly Kings.
Van has gotten some serious skillz over the years, eventually speedrunning the Dungeon once per day, and the 4 Heavenly Kings (also known as the 4 Idiots) have been touched by the feelings of the two and have sworn to protect the friendship, while also constantly arguing about which way the friendship should go from here.
It's a childhood friends story. (Also, the fate of the world may be at stake.)
The cast is great, with many memorable characters. Some of them are more caricatures than others, but it's good.
The world-building is OK, it's clearly building towards something with the whole Hero / Demon Lord metaphysics thing, but the rest of the setting details, like the geography, is more fuzzy.
The humor is great, and also distinct; the author has a theme to explore - childhood friends - and is expertly riffing on it.
Above all, this manga manages to genuinely surprise me with a clever plot twist from time to time.
Approved!