Minwoo Hyun is a normal 11th grade student with a dating skill of a jam jar, who is a game maniac crowned as the best gamer in the country, with unparalleled skill in fighting games. A few days after an accident during a fighting game called Metal Heart 2 that Minwoo has played by coincidence, the heroine of the game, Sia Min, appears right before Minwoo's eyes! (In reality, a mega-corporation called MegaTech, maker of Metal Heart 2, has employed a battle android into the real world to collect data.)
However, because of the 'incident', Sia has a personality of a girl from a dating sim game, and she thinks Min Woo is the main character of that dating sim game. It's hinted that something bad is going to happen if Sia gets jilted by Minwoo. So Minwoo reluctantly accepts this 'unique' situation and with the help of MegaTech's special agent Nuri Han, playing the part of Minwoo's 'childhood friend', they begin their adventure to make Sia's dream come true!
Metal Heart provides examples of:
- Barbie Doll Anatomy: Sia is missing certain features but this is justified since she's an android.
- The Bully/Heel–Face Turn: Before Inhyuk became friends with Minwoo, he used to be his main bully until Minwoo saved Inhyuk from a big guy by beating him with a broken fighting game machine.
- Cooldown Hug: Sia gave Nova one after the later lost to her and entered a Super-Power Meltdown.
- Curb-Stomp Battle: Any one of the EA series vs. tanks, MegaTech's personnel, the US Navy, and/or a hoard of students. No casualties but a lot of broken bodies and equipment.
- Cute Witch: Fairy is a pigtail-wearing witchnote who owns a Flying Broomstick named Tock that acts like her Magic Wand.
- Date Peepers: Mina and Yura did this to the group date of Minwoo, Sia, Inhyuk, and Nuri for their own reasons.
- Dating Sim: The Genre of the Metal Heart + game that is what Metal Heart 2 was based on and the type of game Minwoo is bad at and now has to play a real life version of it with Sia.
- Embarrassing Nickname: Goonyung Song's is Dong Gu Mong which means 'anus' and hates being called by it.
- Executive Meddling: An in-universe example to help Minwoo with Sia but there are others in MegaTech who are not as patient and sends the other EA units to fight with Sia in order to retrieve her.
- Fighting Game: The genre of the games Metal Heart and Metal Heart 2, the type of games Minwoo is best at.
- Goggles Do Something Unusual: Minwoo was given special glasses by Megatech to help him by transmitting information to him.
- Good Angel, Bad Angel: Minwoo had this when he was thinking over whether or not he might be inconveniencing the girl he made cosplay as Metal Heart 2's heroine, Sia.
- Groin Attack: Brute Lee was victim of this when he tried to fight Sia to make her join the Kung Fu Club. His legs were shorter than hers.
- Ignored Enemy: Sia ignored Park Chanoh's pitch, Anaconda King, because she does not see the point in hitting it.
- Important Haircut: Nuri used to have long hair until after her mother died and before she asked her father the reason why the people tried to kidnap her.
- It's Not You, It's My Enemies: Sia tried this to get away from Minwoo to protect him but he convinced her stay.
- Kid With The Remote Control: Nuri is this for Minwoo's protective vest. Minwoo is implied as this for Sia during "battle mode".
- Lethal Chef: Nuri, her attempt at a lunch for Minwoo is censored with the only recognizable ingredients are a twig and tentacles.
- Magic from Technology: Fairy has a broomstick that has the ability to enhance anyones desires in order to make them lose their judgment.
- MegaCorp: MegaTech, the creator of the Metal Heart series, who have other divisions besides the game industry like a weapons R&D.
- Missing Mom: Nuri's mother died.
- Mistaken for Gay: Goonyung Song thought this for himself after a misunderstanding after he lost to Minwoo in judo.
- New Transfer Student: Sia and Nuri both transfer to Minwoo's high school. Nuri actually used to go to the same school the year before but transfered out due to some "complexities".
- Not What It Looks Like: Many instances
- Mina walked in when Nuri was trying to remove Minwoo's underpants.
- When Nuri went to check on Minwoo in the chamber she saw Yura fainted on top of him.
- One year before the start of the story, Inhyuk walked in the infirmary and saw Yura on top of an unconscious Minwoo taking off his clothes.
- Powered Armor: In the minimal sense, MegaTech gave Minwoo body armor to protect him from impacts and has a shock feature that Nuri has the remote control to, in order to revive, help, or punish him.
- Power Gives You Wings: The EA units gain these during their Super Mode/Super-Power Meltdown.
- Ridiculously Human Robot: Sia and the other EA units. They think they are the characters from the game and don't even know that they themselves are robots.
- Right Behind Me: Minwoo tells Inhyuk how he plans to make Mina cosplay as Sia, but Mina heard him.
- Shower of Awkward: The day after Nuri's house burned down, Minwoo saw her in this situation when he entered the bath after he woke-up.
- Sibling Terminology: Mina calls her brother Minwoo "oppa", Korean for brother.
- Something Else Also Rises: This happened because Yura was too close to Minwoo while trying to find a way out.
- Super Window Jump: Nova was in a jug that smashed through the shop's window before she broke out of it.
- Spell My Name With An S: Due to the rather inconsistent roman spellings for Sia's name, it comes out as Sia, Shiah or Siah.
- Tron Lines: The EA series have them on their body when they go Super Mode.
- Verbal Tic: Nova ends her sentences with "nya."
- You Are Number 6: Sia is number in 7 the EA series. Nova is number 5.
