Ok, I feel like I should write this after reading the webtoon.
a) So, your boyfriend/girlfriend cheated on you ?
Yes, you deserve to be cheated, it's your damn fault not his/her fault. Even the sanitizers bottles say it will kill 99.9% germs not 100%.
b) I love him/her very much and we had been in relation for years.
Who said to love ? Your parents or something? You fell in love him/her and it is your fault, not his/her.
c) What to do now ?
Get inside your room, lock it for weeks, play games, swipe some old memories, message your beloved gf/bf in the hope he/she will return (damn I am not writing the full forms anymore) and if possible, nominee someone (if you want).
d) Should I give him/her a call (I love him/her ?
Your mobile, your time, call whoever you want to call. He/she may pick it up.
Okay in serious note
Do not give a damn call, do not apologize nor door for him/her.
If possible, take revenge (He/She deserves it). We got some nearly 7,777,504,748 (Approx.) on earth and more people outer space, you will find your match one day or else some sites are there.
*** How to take revenge?
You have to become a stalker, follow him/her around, if possible, nearly a week, get some photos/video of his/her with other gfs/bfs.
After then, make some collage photo, some sideshows of you and him/her along with his/her ******
Get them uploaded in some clouds and share them in public and if possible get some hard copies and throw them on his face in public, and let some people them to their home.
Btw do not forget to write his/her name, phone number and address. (It will be like adding petrol to fire
Anyone can make a mistake.