KONO Tsuranori 
D-Genesis: Three Years after the Dungeons Appeared Volume 7 [EPUB ebook] 

What’s mine is yours, and what’s yours is…miner? Keigo and Miyoshi rack their brains over what to make of the stunning revelations they’ve received about the dungeons’ origins, but before they have everything ironed out, a new wrinkle appears: someone else has obtained a Mining orb, and there may not be enough time to sanction its use before all mineral drops in Yoyogi Dungeon are set to useless ores! Gathering Mishiro and gemology maniac Komugi, D-Powers dive into the dungeon in a race against the clock. They’re aided by a second batch of fluffy familiars. Meanwhile, another one of D-Powers’ experiments bears…fruit?