Many thanks to크산티페 from the DC Elsword gallery site for writing up this good summary.
Current Timeline of CloserS – Year 2020
[Some tens of years before the start of <CloserS> – Dimension War]
Dimension Gates started opening in various places on Earth and Dimensional Monsters(DMs) appear from those gates and attack humans causing heavy damage.
A Psychokinetic energy is emitted from the Dimension gates whenever they open. These PK energies awakened some humans to psychic powers.
These psychic humans are named ‘Closers’ and they contribute greatly in suppressing the monsters and closing the dimension gate.
After the crisis has subsided and the Dimension War was over, UN creates an organization called the UNION to train Closer agents and deploy them around the world.
At the same time they install ‘Psychic Energy Suppressors’ in many places around the cities to prevent Dimension Gates from opening. (Currently, the Suppressors can prevent 99% of the Dimension Gates from opening)
But they cannot afford to install those Suppressors everywhere so Closer agents go and handle the situations in places where Suppressors don’t exist.
※ Known Dimension War participants
J – One of the first Closers. Special agent of the Dimensional response squad ‘Wolf Pack’. Possesses significant Psychic power and was involved in many secret missions. Because he participated in lots of secret missions, most information regarding him has a very high security lock.
Seha Lee’s Mother – Legendary Closer agent that ended the Dimension War. Currently retired. Don’t know if she gave birth to Seha after or before the war.
※ Guro area during the Dimension War
Giant DM appeared in Guro but was defeated. Massive psychic energy was emitted from the monster as it was defeated and those energies still linger around Guro area to this day.
Because of this, it becomes illegal and dangerous to live in the Guro area.
J retires from health problems
UNION scientist ‘Kalbach Tux’ performs experiments to open the Dimension Gates without UNION’s permission.
The experiment was a failure but Kalbach was able to meet with the high ranking members of the DMs ‘Ash’ and ‘Dust’.
Ash and Dust modifies parts of Kalbach’s body into that of DMs. Kalbach gains powers of DMs and murders many Closer agents before being captured.
After, Kalbach was imprisoned in a research center to be experimented on.
Seulbi Lee lost her parents during the Dimension War. She grows up in one of UNION’s institutions.
Because of her extreme efforts and practice, she possesses twice the abilities of her colleagues.
Yuri Seo’s father loses his job. From then on, Yuri becomes very sensitive to problems regarding jobs.
Yuri had superior physical abilities since young age. She won the national Kendo tournament.
Seha Lee had a strong Psychic potential since he was young but isn’t interested in working as a Closer agent. In his school, he’s an infamous for being a game addict.
Kalbach Tux escapes from the research center. He hides in one Shopping Mall in Gangnam and continues his experiments. His experiments succeed and DMs are summoned.
The shopping mall where Kalbach carried out his experiment already had the Psychic Suppressors installed.
Closers handled the DMs that appeared but this incident where DMs appeared regardless of the Suppressors remains a mystery
Yuri Seo awakens to her Psychic power. Normal Psychics awaken from a very early age but Yuri is a special case where she awakened at 15 years of age.
[Year 2020 – Current]
Dimension Gates start shaking in various areas again and UNION becomes very shorthanded for Closer agents. UNION develops a plan to deploy underage Psychics.
J is recommended as the underage team’s supporter and returns. In Seoul a 5 member team named the ‘Black Lamb’ was created with Seulbi Lee as its leader. Kim Yujeong is assigned to command and manage the newly formed team. The reason why each member joins the Black Lambs is as follows: Seulbi wanted to stop another Dimension War from happening(guess), Yuri wanted to get a job in civil service, J ran out of money he had saved up and for Seha, his mom forced him to join.
DMs that are resistant to regular bullets appear in Gangnam and police are being pushed back.