In the beginning of online dating, the girlfriend turned out to be her sister's best friend

Lin Yi was reborn into a parallel world, a boy with terminal cancer who was in his freshman year, and also had an online girlfriend, Luo Ying Bun.
Falling English: Let's run now, shall we?
Lin Yi: Ben now?Running now is impossible!Love is impossible in this life!
"Ding! God-level perfect life is successfully bound. As long as you complete the task, you can get various rewards, and there is hope to cure cancer."
Lin Yi: This...cough, in order to survive, for a better life, I am very willing to come here!
On the day he was running, he looked at Mu Zilin, his sister and best friend who was gentle on the surface, but violent and fierce, "Sister Mu? Why are you here?"
Mu Zilin: "Silly brother, I'm here to show up with you!"
Lin Yi: …
Run now?You don't have to be in love!Run away, never fall in love with a tigress!
Mu Zilin: Let's see where you are escaping!
System: "Ding! Post the mission and give Muzilin a kiss. If you don't complete the mission, cancer cells will explode."
Lin Yi: Why is it so hard not to fall in love!

Key words of the novel: In the beginning of online dating, my girlfriend is actually my sister's best friend. No pop-up window. In the beginning of online dating, my girlfriend is actually my sister's best friend.