The reason Ren Xiaosu decided to save Luo Lan was because he intended to try to get into Stronghold 109 through Luo Lan!
Earlier, Ren Xiaosu noticed Luo Lan and the soldiers were getting along great. Moreover, he could feel their support for Luo Lan and Qing Zhen. People that well-supported must have something extraordinary about them. So Ren Xiaosu had been thinking if this lifesaving favor could resolve the enmity from before. If he couldn't resolve it, it would not be too late for Ren Xiaosu to personally kill Luo Lan. He also thought about whether to conceal his identity by using another name, for example. But after thinking about it, Ren Xiaosu rejected the idea, because Luo Lan had seen Yan Liuyuan and Xiaoyu before.
"Brother, give me a hand!" Luo Lan wiped his face and said, "I can't get out of the vehicle myself."
Ren Xiaosu pulled Luo Lan out of the vehicle. "Let's leave quickly. The Experimentals will break through the defensive line soon."