Yu En is the patriarch of a Shanghai-based conglomerate and grandfather to siblings Shenmei and Jun Shī, both of whom served in US military capacities. Following Jun Shī's extraction from the Penamstan warzone by the Mad Dogs unit, Yu En orchestrated Jun's covert transport out of the country. Jun was severely disfigured and in a vegetative state due to a viral infection. Yu En brought him to the family mansion in Shanghai, personally overseeing Jun's care while relentlessly seeking a method to halt or reverse the virus consuming his grandson.

In 2006, Shenmei arrived at the Shanghai mansion after escaping a compromised safe house, escorted inside by Yu En's secretary, Hao Ran. Yu En was recounting a story to Jun to comfort the bedridden soldier during this encounter. Shenmei acquired critical information and later received a vital data chip from Yu En; this chip had been embedded within Jun Shī to monitor and record his physiological condition.

The mansion subsequently came under attack and was bombed. Hao Ran was crushed by falling debris during the assault. Yu En perished in the destruction while physically embracing Jun Shī, shielding him in their final moments. Yu En's documented presence remains confined to this specific narrative.