This could be interesting.
Do Minjoon is too smart to allow any slight mistake of being noticed by us mere humans in his 400 years of stay on earth. So even if it was the 'special space military unit' (ala MIB) headed by CaptYoon Shijin, he would be fly under the radar.
But they would probably try to get him after Manager Do outed himself, after he teleported Songyi out of the restaurant to the hospital after she was poisoned. The special space forced would fly straight to the hospital with Big Boss as leader. And while in the hospital, the one who is in charge of the ER would be doctor Kang Moyeon.
As Manager Do tries to revive Songyi, Moyeon would try to get in the way of the 'intruder'in the ER, and will get the shock of her life as he recognizes Manager Do, as her sunbae, who is also her first love but 'died' a tragic death years ago.
And the foursome meet in the hospital, as Minjoon will get things to fly around him and barricading himself as he tries to save Songyi. Shijin will come blazing in trying to protect the people and capture the alien, and whike doing that he will princess carry Moyeon out of the ER, since Moyeon is still in shockat seeing MinJoon.
And this is where the cliche kinda Love-square will happen.
And that is You who Came from the stars is the Descendant of the sun.
What if... Goblin and Hwayugi was one drama... would Kim Shin, Grim reaper, Ogong, Hwichul have a drink together.. and where, how, and what would they eat/drink. And who would invite who... ?