Shirou in Another World.

Volume 2: Black and Red Clouds CH6

A few years later.

A 13-year old Shirou dashed behind Lunea as she sped through the underground passageways. The smooth walls on both sides flashed by his reinforced body, the flapping Akatsuki uniform ahead of him suddenly stopping to sniff the air.

He knew his nose was good with magic, but Lunea's ability to smell magic was in an entirely different league. Then again, Shirou was comparing his ability to that of a phantasmal beast.

There was absolutely no chance he would win.

Lunea picked the path branching to the right, with Shirou following close behind. A tremor suddenly shook the underground passage, a result of the battle ongoing above. The guards of the hidden base were being drawn out, while the non-combat personnel bunkered deeper.

With all those people packed together in the deeper levels, Shirou and Lunea would have a field day simply "clearing out" the rats.

The only threat was the leader of the hidden research base, Kabuto. But the group knew that he hadn't been around the base for a few years, which only played further into their cards.

Lunea jabbed a hand forwards, willing the ambient mana to grow unstable, forcing the traps that lay ahead into activating, or destabilizing from the sudden instability of their environment. A few explosions occurred, some flying shrapnel, kunai and shuriken appeared from the walls directed at the pair.

Shirou traced some kunai and shuriken in return, shooting them to deflect the projectiles from hitting the duo. Once the threat was gone, the traced weapons disappeared, leaving no evidence behind.

Any investigation of the area would appear as if the traps had malfunctioned for no reason.

But the plan was not to confuse the enemy. Shirou and Lunea's intention was to infiltrate the base and rescue the prisoners, then eliminate the people in charge of the base.

Everyone else associated with them was free game.

Shirou and Lunea were determined to let none escape. Not after the glaring evidence of human experimentation from multiple sources.

With careful information gathering, the group of four had found the location the base was hidden. No blueprints had been leaked, so Shirou and Lunea had to improvise. The endless tunnels were impossible to track, but Lunea's sense of smell was that of a phantasmal beast. Which cut down a lot of problems Shirou would normally meet.

One floor down later, Lunea notified Shirou of their first breakthrough.

"There's a few guards here. They seem to be guarding a room."

"Are you sure?" Shirou knew that any personnel should've evacuated below already. He wasn't expecting to meet any this early.

"Yes, I smell a lot of dead bodies inside with them."

Shirou grimaced. The unfortunate souls must've perished in the worst way imaginable.

"When we arrive, I'll take the lead."

Lunea nodded. Shirou was good at initiating fights, lowering the risk for them both.

It took them a minute to reach the room. Shirou didn't even bother waiting, slamming the door open and throwing a few runes of light into the room. The nin inside who were caught off guard by the unknown intruders found themselves blinded by the makeshift flashbang, an effect of reinforcing them to the point of breaking.

They didn't survive a second longer as Lunea tore their necks with her claws.

Dead bodies slumped on the floor behind her. The wolf quickly made her way to grab the scientist huddled on the floor. One quick glance at the room's contents already confirmed her suspicions.