Rise Of The Evolving Monster: Monster Girl Harem! - Chapter 6: Goblin Feast

I want an S-Rank skill too! I want it so badly, I could die for it![You have awakened an S-Rank skill.] [But it only works when you die.]Eh !? WHAT IS THE POINT OF GETTING ONE IF I DIE !?

Chu Yang, the Ninth Master of the Nine Tribulations Sword, sacrificed almost everything he had for the sake of improving his martial arts, including the love of his life. After spending three years locating the fifth fragment of the Nine Tribulations Sword, he was ambushed by all sides at that very place. Mortally injured with no means of escape, Chu Yang executed a sacrificial technique by plunging the Nine Tribulations Sword into his very own heart. “With the blood of my heart, ten thousand tribulations will collapse!”

After witnessing the death of all his ambushers, Chu Yang’s vision began to darken. At a distance, moments before his death, he saw the mastermind who had plotted his downfall — Mo Tian Ji. With that, his eyes finally closed.

However, with a start, Chu Yang once again awoke to find that he had returned to when he was sixteen years of age! Furthermore, the Sword Spirit of the Nine Tribulations Sword now resided within his Dantian, the energy center of his body! From that very moment, Chu Yang would then begin to right all of his past regrets, and carve his very own legend by fulfilling his destiny as the final Master of the Nine Tribulations Sword, and defeating the Heavenly Devils beyond the realm of the Nine Heavens Continent.

- Description from novelupdates

A mecha otaku is reincarnated into another world as Ernesti Echevalier (Eru). In this world there exist huge humanoid weapons known as Silhouette Knight. Dreaming of piloting those robots, Eru, with childhood friends, Archid Walter and Adeltrud Walter: together they will aim to become a Knight Runner, pilot of Silhoutte Knight.

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.