There's No Love In the Deathzone (BL) - Chapter 59 - 58. Grim Reaper

Sergeant Xia Yao, born into a wealthy and renown ancestry, is a playboy who has turned over a new leaf. Yuan Zong is an ex soldier from the special forces who opened a bodyguard training company after being discharged.

When Yuan Ru, Yuan Zong’s sister fell for Xia Yao’s charms, but could not break down his erected barriers, she came to Yuan Zong for assistance. Little did she know, the moment Yuan Zong saw Xia Yao, this ex-special force knew no other person would ever catch his eye.

And so begins the battle between brother and sister for the most coveted price – Xia Yao’s heart.

- Description from Novelupdates

“Keep it in your mouth… Swallow it… Baby, be good…“

I, Lin Yun, with my exceptional aptitude, had thought that I would be trained as a key disciple, however...“The Demon Sect will never expect us to send such an excellent disciple undercover. Once you attain a high position within the Demon Sect, with our help both from within and without, why would we worry about the Demon Sect's destruction?”Three years later.“The Righteous Path will never expect us to send such a promising disciple undercover. Once you attain a high position within the Righteous Path, with our help both from within and without, why would we worry about the Righteous Path's destruction?”Lin Yun: I just want to quietly cultivate to immortality...

The second prince has come of age. To celebrate the advent of such an occasion, the search for a suitable bride began. My younger sister was expected to go to the Royal Palace as a candidate. However, despite this, she eloped the day before her departure. I, the older sister she left behind, looked almost exactly like her – so much that we were often mistaken for twins…

One month, right? For just one month, shall I substitute in for my sister?