"I think it's normal and common for teenagers to have sex since many of my peers also do the same," the HCMC boy says.
"However, I just learned that there is great risk of contracting STDs, which I had no idea about."
He is one of an increasing number of Vietnamese teenagers engaging in early sexual activities, believing that sexual desire during puberty is normal and indulging it would help satisfy their curious minds.
According to a 2019 study by the Ministry of Health and World Health Organization on student health behavior, the rate of having sex before the age of 14 had more than doubled to 3.51 percent from 1.45 percent in 2013.
Only 42 percent used condoms while 44 percent used other birth control methods, both much lower than in 2013.
A 2018 study by the National University in Hanoi found that around 10 percent of Hanoi students had sex before finishing grade nine and 39 percent before graduating high school.
Around 10 percent of high schoolers admitted to having sex with more than three partners.
On a Facebook community group, around 100 admitted they had sex for the first time while in secondary school.
Many students claim that since sex education in school is taught in a theoretical manner, they try to sate their curiosity and get first-hand experience by watching pornography and engaging in unprotected sex.
Nguyen Van Thanh had sex with his girlfriend at the age of 16 for the first time and has been keeping it a secret from his parents. Like Tuan, he also says his school did not teach or equip him with knowledge about how to protect himself from STDs.
"I didn't use a condom because I had no idea how to.
"At school, we only learn about body parts and about reproduction via biology textbooks.
However he thinks having sex at this age is totally normal and that kids in many countries do the same, and says he frequently goes on apps to search for sexually active girls.
Many Facebook groups with thousands of members have become places where underage people openly share their sexual experiences.
Several of them admit to having sex with numerous partners before the age of 18.
Tran Xuan Quoc, 11, went online and used phone apps to learn about sex after hearing many older students talk about the birds and the bees both online and in person.
"I am intrigued. I think I will try it out when I am a bit older to see what the hype is about."
While many people point to early onset of puberty for children developing interest in their bodies and sexual behavior at such an early age, some blame it on stress children face.
"I think students face a wide range of stressors related to academic demands," Dang The Danh, the father of a high-school boy in HCMC's District 3, says.
Tran Thanh Nam, a psychologist, says 20-30 percent of children have anxiety and depression and feel disconnected from their parents, and "so having sex is a way to take their minds off everyday stresses."
"Romantic relationships assist them in seeking connections, particularly when they are unable to connect with their family members and feel lonely in their own home."
Tuan finds that having sex with people his age gives him more people to talk to since he is depressed due to his parent's broken marriage.
"After they divorced, I had no one to talk to. I believe the girls I have sex with listen to my stories and make me feel better."
Another culprit is the ease with which young Internet users can meet, talk and connect with a large number of people these days.
Nam said: "Many modern teenagers learn about their rights but forget that rights always come with responsibilities."
One of the factors contributing to teen abortions is the country's attitude toward sex and reproductive health.
Every year Vietnam has 300,000–350,000 abortions, more than any other Asian country. According to the health ministry's department of population and family planning, the actual figure could be even higher because it does not take into account illegal cases and those performed outside clinics.
Young women between the ages of 13 and 19 account for 62 percent of all unexpected pregnancies.
Though there has been progress, experts say Vietnam must do more to improve sex education in schools. Reluctance to bring up the subject has been a persistent issue both at school and home.
Dr Vu Thu Huong, a former lecturer in the Hanoi National University of Education’s primary education department, says sex education programs are being neglected and taught too late.
Besides, the content is not appropriate for students, she adds.
Nam advises parents to start teaching their children about sex at a young age.
"You might think a child is too young to get sex education. But it's never too early to talk about sex to your kids."
He says a child should be able to tell the difference between boys and girls by the age of three.
"If a child feels embarrassed when we discuss sex education with them, they have read about it elsewhere, and they will no longer listen to their adults because what we tell them may be less interesting than what they already know."
Dr Le Duy Thao of Hong Ngoc General Hospital's department of andrology says many parents avoid teaching their children about sex or do not fully explain. There have been no studies in Vietnam on the frequency and effectiveness of children discussing sex with their parents. However, many teenagers claim that sex is still a taboo subject that they never discuss with their parents.
"I've never told them I've had sex," Tuan admits.
"I can't imagine discussing my sexual activities with them since it would be very awkward."