I think he was basically doing what he wanted in Negima after a few volumes in, not counting the rushed end.
Different casts and different focuses is likely the reason why things are getting different here. This one is about immortality including it's downsides, and a group that deals with the nasty underbelly. So you have them fighting black market mercenaries attacking slum residents, zombies, and so on.
There's some similarities to the magic world part of Negima, especially the early bits of it- when characters got impaled through the shoulder or cut-off arms, and the crew was scattered so there was a good sense of worry.
Ken continues to build comic to comic. There's normally hints of his next comic later on in his last (like, late in Love Hina he started developing the martial arts more, for example).
Things are just going from bad to worse. Kuroumaru's been possessed and Touta got gravely wounded by him. Sayoko also pulled a Queen Xenomorph on Ikku, the way she kept saying "Why?" while contorting her body is just beyond disturbing, and the whole planet is now in danger! Santa's caring a pretty heavy burden as well.
Man, where is Eva-chan when you need her? Santa is fortunately no slouch but the deck is heavily stacked against him with Touta being incapacitated, Kurōmaru is being manipulated, so is Kirie, and Ikkū is out of action. Further more, Santa's good memories of Sayoko are making him feel conflicted. Things went from worse to much more worse.