"It had always been my intention to return home at some stage and the offer from North Harbour probably hastened that decision. It was a great opportunity to play at a different level and one I felt I just couldn't let go," Manning said.
The 22-year-old has been contracted to Munster for three of the four seasons he spent in this country and since making his debut in September 2005 has played 32 competitive matches and was on the Heineken Cup-winning matchday squad in May 2006.
"I've enjoyed my time with Munster, appreciated all that I've learned. It certainly wasn't an easy decision to decide not to accept a further contract. But I didn't want to be looking back in years to come and wonder how I might have fared in NPC."
Academy player Cronin was offered a Development contract for next season but opted instead to take up a full-time contract with Connacht, a decision that Munster support as their chief executive Garrett Fitzgerald explained.
"We believe that to further his progress, Sean needs to compete on a regular basis at representative level and at this stage a move to Connacht is in his best interest. We wish him the very best during his time with Connacht," Fitzgerald said.
Former Ireland Under-21 international Denis Fogarty will continue to share the hooking duties at Munster with internationals Frank Sheahan and Jerry Flannery. Fogarty has just renewed his contract with the province, while back rower Michael Essex is expected to accept a Development contract.