Aphel

Because Hyesung smiling back at Woojin is IMPOSSSIBLE. If your older twin replaces you all semester, would you, the younger twin, smile back at a classmate 18 years later?
I can acknowledge the different seasons, but younger twin Hyesung and Woojin were physically at the river at the same time ONCE because Hyesung reacted to Woojin's rock throw.

2026 Hyesung time-traveled back to 2008 and replaced 2008 Hyesung before he met Woojin, as the latter said, "You know me?" at the locked classroom, which is their first encounter in that timeline. 2008 Hyesung returned after 2026 Hyesung saved Woojin, and studied abroad soon after to pursue his dream as an artist. So, 2008 Hyesung technically did not meet Woojin at all. The montage at the river could be interpreted as parallel worlds, but Hyesung did react to Woojin's stone-skipping throw, meaning they met at least once, and with 2008 Hyesung not knowing who Woojin is personally, he stared at him coldly, with Woojin looking dejected afterwards. Either way, Woojin waited for years for his Hyesung to come back.

Hyesung placed the restriction on Woojin, but not on Taejun. So, he somehow befriended 2008 Hyesung offscreen, maybe giving him the picture, serving as a bridge between the two. 2008 Hyesung knows Woojin exist, but does not know him intimately. I do feel it is a bit weird to keep a picture of a stranger, but with Taejun in it, I guess he framed it as a memorabilia after 2008 Hyesung became friends with him, or all Hyesung versions will always have some affinity towards Woojin whether consciously or unconsciously.

I am guessing Woojin survived the accident because Tae Jun was there and was on foot instead of on a bike. For the rest, 2026 Hyesung disappeared from the 2008 timeline and returned to the present after saving Woojin, but 2008 Hyesung still exist without ever meeting Woojin as they showed the memories in reverse order when 2026 Hyesung woke up in the present day. 2008 Hyesung continued his life overseas while still being friends with Taejun. The letter 2026 Hyesung wrote to Woojin explicitly said to pretend they do not know each other and Taejun and Woojin honored that. It would be too complicated to explain to 2008 Hyesung what 2026 Hyesung did without sounding crazy. So fast forward to 2026, 2026 Hyesung woke up, replacing 2008 Hyesung, and still became a famous artist. Woojin showed up to Hyesung's gallery, left the stone in the hopes that Hyesung recognizes it because only the 2026 version knows. Unbeknowingly, Woojin met Hyesung at the river a couples times before throughout the seasons, and always smiled at him because he knew if Hyesung smiled back, it would mean that the 2026 Hyesung that he loved came back as written in the letter. So, in the end, when they reciprocated, Woojin and Hyesung finally met again.

The ending is much like X-Men Days of Future Past. The JHS with the time travel memories just arrived in the present timeline. The JHS between the disappearance after saving LUJ and before the time travel exist, but does not remember him intimately. So, LUJ meets and smiles at JHS twice before, but knew if he did not reciprocate, he was not the JHS that he loved because of the letter. So, at the end, when they smiled at each other, they finally meet again.

The thing is, the name Tan ZaoZao does not exist in the real world. Either the "Tan ZaoZao" we know created this username for her character in the game world, or JiuShi invented the name because it's his dream, not knowing her real name.

Interesting.. Maybe I watched it with poorly translated subs, but wasn't Ruan Lan's objective to "purify" the game before it got tarnished, and not delete it from existence?
If the Spirealm did get erased, shouldn't Zao Zao still be an actress, and not a live streamer, because she was in the industry for 10 years? His childhood friend being in economics instead or gaming is weird after all the memories between Jiu Shi and him. Maybe its simply a plot hole, rushed ending or something. 🤷‍♀️

The ending just destroyed the entire story into pieces, because every character decisions that made them loveable was only a fragment of Jiu Shi's dream. I wish they made the Spirealm real, and see the consequences come into reality, not be reminded by the most cliche Wizard of Oz ending (I swear JS's face was screaming "And you were there" to every character he remet).