Anybody who says this is jumping the shark has not been reading this manga. This manga is like Jitsu wa Watashi wa, the shark was cleared in the first few volumes. This manga is way above the shark, it's left the fucking stratosphere and is hurdling towards the edge of the observable universe and anybody who hasn't realized this happening over the past 100+ chapters have not been paying attention.
This manga is absurd and always has been. Hope this isn't what I think it is and the manga will wrap up in a chapter or two but seems like it. If not, this whole thing is a massive joke to parody time travel clichés.