There was something missing in Yusei Fudo.
The people he knew and talked to saw this…but not because the absence of it was noticeable. Rather, it was when it came back that they noticed it was gone in the first place.
After Team 5Ds split up, he never moped. Instead, he lived life to the full. Like his father before him, he worked at the reactor .He continued working as a mechanic, making house calls. He sometimes went to duel academies, and took over some of their lessons. He even participated in a few local tournaments.
So it's not surprising that nobody noticed what was missing from him. But when it was there, it was noticeable.
Noticeable when he watched crow, Rua and Jack on TV.
Visible when he could be persuaded to relay anecdotes about them all.
Obvious when a local kid went around to his house for help with their homework and he was sitting on the sofa talking on the phone to Aki Izayoi.
When these things happened , the people would see that his eyes lit up.
And that was the thing which was missing.
The light.