Wouldn't Kiriya already have won on page 22, when Majin played the same tile he'd end up ron-ing? And doesn't that also means he's in furiten or something?
Furiten only takes into account
a) when you folded a winning tile before - meaning you cant call on it later for ron, only draw it yourself for tsumo.
b) if someone folded your winning tile but you passed it on during that turn (until it's your turn again)
There is an additional Han for winning on the last tile, hence why he got a Mangan out of it. (Mangan being the first guaranteed point total threshold - 8000 - at 5Han. You can achieve Mangan with 3 or 4 Han if your Fu is enough.)
In this case he had 3 Han from the Dora triplet, 1 Red tile (those counts 1 Han each in the variants they are used in) and the final Han he got for calling there.
Majin is impressed by Kiriya reading that far into the situation, being able to snatch up potentially crucial additional points by guessing Majin would drop a pair of red dragons to have a safe runout towards the end.