The Magic Academy's Physicist - Chapter 6: The Helper For Freshmen

Nagasawa crossed to Naruto Universe and was bound to Konohagakure.

If Konoha is severely damaged and destroyed, Nagasawa’s lifespan will be reduced.

He panicked at the thought of the upcoming Nine-Tailed Demon Fox’s attack , and the thought of Konoha getting destroyed left him in despair.

Fortunately, while bound to Konoha, he can obtain templates of powerful characters.

At the beginning, He got the Whitebeard template! Since it’s the Whitebeard from the Summit War of Marineford, he can use Tremor-Tremor Fruit’s ability and Haki.

Facing the Tailed Beast Ball, which terrorized Konoha Shinobi, Nagasawa leaped and shattered the Tailed Beast Ball with one punch!

- Description from Novelupdates

Another entry in what you can call the Proto Harem Series: the books written before the Harem Series that take place in the same world.

It’s about a swordswoman whose student is captured, so she goes to rescue her.

The Fourth Shinobi World War is over. All enemies are defeated. Finally, a long peace reigned in all countries. The Seventh Hokage laid down his arms and lost all his Youth Power. One dream, the goal for which he spent his whole life, has been achieved. His path is over. Is this really the end? Could it end so easily? What if the Savior of this World turns into an arrogant and cunning ruler?Perhaps no one would ever have been able to predict such a result. On that day, everything changed ... Countries, riches and power, the most beautiful women and their young daughters - he will subdue them all! The Seventh Hokage with the strength capable of conquering the heavens chose a different path, now he will take everything for himself and pave the way to absolute world domination!

A major event happened recently to the demonic sect – their powerful sect master suddenly went missing.

Everyone comforted each other: “Don’t worry, the sect master must be out pursuing fun, and so on.”

“Well, that makes sense.”

They waited.

Waited and waited.

Waited and waited.

Waited and… Everyone slammed the table: “We’ve waited so long! The sect master must have met with a mishap! Look for him!!” Numerous disciples therefore ran rumbling down the mountain.

On a certain day of the month, a certain sect master opened his eyes and thought in confusion: Hey, who am I?

- Description from Novelupdates