there is 2 timeline where wagamatsu travel the first one we saw is what happen if gaku is not there on 2000 timeline we can see that the freshman got their insurection (because gaku isnt there to stop sakaki), and it lead to missing wagamatsu (back to his timeline) and mayor kanamori, it could be a foreshadowing too or "what if" kind a thing, now in gaku timeline i think the question is what will happen to wagamatsu because cleary gaku gonna help him and it leads to wagamatsu isnt go back to his timeline and kanamori will still in charge of aoba, and the burger guy also gaku doesnt know the fact that wagamatsu a time slipper, and its kinda confusing because burger guy said he know wagamatsu when he was middle schooler on his origin timeline where wagamatsu could be a timeslipper to, so basically there is no origin timeline in the first place, because in gaku origin timeline kanamori become a mayor and it requires wagamatsu event he need to dissapear so kanamori left aoba, conclussion in every universe there is a timeslipper