HareGuu (or Hare Guu, Hare to Guu)
by Renjuro Kindaichi
Serialized in Monthly Shōnen Gangan
10 volumes (complete)

Summary:
"After his family inherits some property, 11-year-old Hare, his eccentric mother Weda, his robot assassin Robot and Guu, an adopted child who turned out to be an alien of unknown origin, age or physical composition, embark from their jungle home to the city. After Hare’s mother invites the rest of their jungle friends along for the ride, the party sets out on an airplane piloted by the less-than-confidence-inspiring Alex and his assistant Sherry. But trouble is amiss when Hare discovers that everyone else on the plane has been drugged with sleeping pills and the pilot is headed somewhere other than their intended destination. A sequel to the original Hare Guu manga (Jungle wa Itsumo Hare nochi Guu) , this manga continues the wacky comedic high-jinx of the original."

http://mangahelpers.com/m/hare-guu
https://www.mangaupdates.com/series.html?id=13796

Looking back at this series, it feels like I'm looking at some kind of ancient ruins. The original Jungle wa Itsumo Hare nochi Guu was popular enough to get an anime (which won multiple awards), which was popular enough to get a commercial translation (subbed AND dubbed, and the dub was broadcast on Funimation) which was popular enough for the only episodes that were never commercially translated, the Final OVA, to get fansubbed, yet when the series ended on a big cliffhanger and there was a whole second series of manga which continued right where the original ended off, HareGuu, nobody really did much about it. I believe 2 groups tried scanlating it YEARS ago, but one of them never got past the first chapter and the other one got to chapter 6 but the only links of it I could find led to dead MediaFire downloads.

It's really disappointing to see that the interest in this series, that seems like it was absolutely huge back in the 2000s, has pretty much completely died down. I think I'm speaking for most fans of the original series when I say that the work of anyone who is willing to translate this will be much appreciated (assuming the fans haven't all vanished of the face of the internet). I can provide the raws of all 10 volumes to anyone who is willing to help.