A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Just wanting to know if Pekkle No Oni's 'gain 3 honor' is an entering-play honor gain, thus will not allow the 'gain 2 honor' on Wardens.
I don't believe you can combine the two, but the question needs to be clarified through official channels before I can say one way or another.
Just wanting to know if Pekkle No Oni's 'gain 3 honor' [...] will not allow the 'gain 2 honor' on Wardens
Indeed, you can't use the Reaction on any Wardens in your hand after the first time each turn your Pekkle on Oni enters play, unless your gain of 3 Honor doesn't happen, because this gain is for the card entering play (see below).
Pekkle no Oni's trait reads "After the first time each turn Pekkle enters play: Gain 3 Honor."
Wardens' first ability reads: "Reaction: If this card is in your hand, after you bring a Personality into play without gaining Honor: Attach this card to him (paying all costs). Gain 2 Honor."
Glossary, Honor: "When something checks to see whether a card has entered play "without gaining Honor," this is the same as checking whether any Honor has been gained for the card entering play (see Rules Glossary, "For".) Specifically, Honor gains that are contingent on the card entering play, including the rulebook Dynasty phase honor gain for aligned Personalities, mean the card has entered play "gaining Honor," unless the Honor gain was reduced to zero or negated. However, Honor gains that only come from the same action or trait that brought the card into play, without being contingent on its entering play, do not mean the card has entered play "gaining Honor.""