i remember this part in the novel, I was trembling from excitement just reading it! *sigh* man, the ending is still unsatisfactory to me but more or less the upcoming fights will still be awesome! can't wait for more goosebumps!
here, https://www.lightnovelworld.com/novel/i-alone-level-up-solo-leveling-web-novel
If you mean the chapter where Jinwoo entered the gate it's - CHAPTER 154
...but i recommend to start in CH.150 (the start of this Arc) 'coz u might miss some important details like Cha Hae-In telling Jinwoo about the convo she had with Dead Min Byung-gu and the Prologue of Japan Crisis Arc
I just stumbled upon this and this really give me the feels unlike other smut-shoujo's l've read, pls. update more chaps uploader-san