There's No Love In the Deathzone (BL) - Chapter 748: Side Story 4. Endless Journey - 31

Ye Qiu traveled to the Great Wilderness World and obtained the ten thousand-fold return system.

By teaching or gifting the same thing to the apprentice, you can get a high multiplier crit return.

“Ding, you give your disciple a Marrow Cleansing Pill, trigger a thousand-fold crit, and get a Divine Marrow Pill.”

“Ding, you passed ten years of kung fu to your disciples, triggered a hundred times of critical strikes, and obtained thousand years of kung fu.”

“Ding, you gave your disciple the Zixia Sword, a top-grade treasure, which will trigger ten thousand times the crit and get the Immortal Sword Yunxiao.”

All the disciples: “Master is too generous. He never hides his secrets from his disciples, and he gives everything away.”

- Description from novelbuddy

To take a dragon's hoard is to challenge death.The greatest of the sea-drakes wakes, curled on his silver throne; but there is no silver. His hoard is stolen. He rises, screaming, and chases the thief to the ends of the world—only to be shot from the sky.But dragons do not die easy, and never one with such festering hatred. A dungeon core rises from his corpse.If he intends to survive so near the cove of pirates that slew his past self, he'll need to master his powers—and quickly. For these pirates are dragonslayers; they won't be felled by mere mushrooms or spiders.Beneath the lawless Calarata, the young dungeon core will have to fight to survive; and one day, he will return death to the man who killed him.

Year 2056, in a city in the Yuan Jiang Su Jin area. On top of a ruined, shattered six story residential apartment sits a teenager wearing a combat vest, militaristic trousers, and alloyed battle boots. On his back is a hexagonal shield and equipped is a blood-shadow battle knife. He sits there silently on the edge of the roof. At this time, the sparkling sky was shining and there was a refreshing breath within the air that blew towards him. However, there was only silence within the ruined, deserted city, with an occasional howl that makes your heart skip a beat.

- Description from novelupdates

A side story series featuring the girls of Kyoukai Senjou no Horizon.