My Boyfriend's Sister Is a Man in Disguise

[Female Lead's POV]

After Su Li turned fifteen, her luck was unbelievably good. Though her grades were average, she just scraped into the best high school in the city, then got into a top university by sheer luck.

Her boyfriend was gentle and considerate, always putting her first. Everyone envied how lucky she was!

Her only problem was her most hated nemesis, Lin Ran.

Lin Ran excelled academically and won more competition medals than anyone could count. He'd always looked down on people like her, who got into good schools by luck.

They'd been rivals since high school, and the worst part was that Lin Ran was her boyfriend's older sister!

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After Lin Ran learned they were dating, he either made snide remarks or poured cold water on their relationship.

Her boyfriend fed her ice cream, and Lin Ran made a snide comment.

She went on a sweet date, holding hands with her boyfriend, and Lin Ran spoiled the mood.

Just as the atmosphere turned intimate and she and her boyfriend were about to kiss, Lin Ran stood nearby like a blindingly bright light bulb.

Su Li was furious. She just wanted a sweet romance, so why did Lin Ran always have to ruin everything?

Her boyfriend had always been afraid of his older sister. He obediently tried to soothe her. "Baby, my sister's just cold like that. Don't be mad, okay?"

But Su Li couldn't let it go. She was going to settle things with Lin Ran once and for all!

When she barged into Lin Ran's home, she found him wearing nothing but a bath towel, his eight-pack and V-line on full display.

Su Li's nose started gushing blood. Her boyfriend's older sister was actually a man!

[Male Lead's POV]

When Lin Ran was fifteen, he was inexplicably bound to a System. He learned that he was in a book, and the male lead was his younger half-brother, three years his junior.

As the female supporting character, he had to guide the rebellious boy onto the right path and raise him to be a well-rounded student. Only then could he bow out once the female lead who had transmigrated into the book arrived.

Lin Ran was stunned. He was a female supporting character in a book?

But he was a man!

The System apologized. It had bound itself to the wrong person, but the programming couldn't be changed, or both he and the System would be erased.

So Lin Ran had no choice but to disguise himself as a woman and carry out the mission as the original female supporting character.

As a woman, he became the male lead's older sister and began enthusiastically teaching his rebellious twelve-year-old brother to be a positive and upright person!

After completing a task, he looked at his empty bank account and asked the System, "Didn't you say I'd get a reward for completing tasks?"

The System sheepishly explained, "Because you were bound by mistake, your rewards for every task from now on will go directly to the female supporting character."

Lin Ran was speechless. So he did the work, and someone else got the reward.

Later, Lin Ran met Su Li, the female supporting character who knew nothing and thought she'd simply been lucky. He couldn't hide his resentment.

Whenever Su Li congratulated herself on her good luck, he couldn't help making sarcastic remarks.

They became bitter rivals.

In his senior year, he discovered that his brother, now a freshman, was dating Su Li. Knowing the two could never work out, he urged them to break up again and again.

Who knew that an enraged Su Li would barge into his room and discover that he was a man...

[Reading Guide]

1. The female lead and her ex-boyfriend were in a relationship with an age gap: she was three years older. Aside from hugs, hand-holding, and kissing, they did nothing more intimate.

2. The female lead and male lead are the same age. She only gradually falls for the male lead after breaking up with her boyfriend.

Blurb written on March 25, 2025, revised on April 21, 2025, and saved as a screenshot.

Theme: Love yourself every day.