Oreki may as well be Tomoya and vice versa. They have the same seiyuu and behave and think in largely the same manner. The main heroine in both shows is also there to serve as a foil and contrast for the protagonist and the style and tone of the two anime is very much similar. While Clannad is much more serious and dramatic than Hyouka is, there's something for fans of either show to enjoy here.
Apathetic guy steps in to save a club from termination and ends up more involved than he ever intended.
Same style of a main character. Tomoya doesn't care about anything and tends to avoid useless things, same with Hou. They both start to open up though through the same means.
Both KyoAni, same seiyuus for both lead male and lead male's best mate. Similarities in pacing and lead male's general attitude.
The protagonist in Hyouka reminds me of Tomoya from Clannad a lot. They even share the same voice actor. Not to mention the animation style in Hyouka looks reminiscent of Clannad, very smooth and of high quality. Hopefully from now on KyoAni will go back to making anime with animation of this caliber.
-Both, male and female protagonist have very a like personalities.
Males are not-of-my bussiness characters that eventually joins a club
Females are shy but perseveran characters that, somehow develope a relationship with the male character (more obvious in Clannad)
-Male deuteragonist (Sunohara in Clannad, Satoshi in Hyouka) are very alike in art and personality.
Male lead and his best friend have the same relationship and similar personalities. Both involve romance, though Clannad is more focused on it. Both are slice-of-life, school anime for the most part. The biggest difference is that Clannad doesn't crush your dreams in the last 30 seconds.
Both of the main characters are lazy and have a little consideration on their surroundings, however a certain person appears in both series and moved them to act. The female main heroine from these series which had supported the MC are both cute, innocent, and elusive. As the story began, both series may appear as an ordinary slice of life, but the storyline becomes more solid in the later episodes which is attractive.
Both series are absolutely magnificent to look at, both designed by Kyoto Animation. Primary male protagonist are voiced by the same voice actors. Both plots involve revitalizing a dismantling club and future character interactions revolve around that club. Rather than incorporate tragedy and supernatural elements with a substantial amount of romance, Hyouka focuses on commonplace mystery scenarios and drama with little romance.
The main characters in both series are quite similar in terms of personality and behavior. Okazaki Tomoya, the lead male protagonist in Clannad, is a lazy bum that never tries too hard at anything and always fools around with his one buddy, Sunohara Youhei. Oreki Houtarou, the lead male protagonist in Hyouka, is a lazy student that believes in conserving energy and leads a dull and passive lifestyle. Like Tomoya, he has only one friend: Satoshi Fukube.
Furukawa Nagisa, the lead female protagonist in Clannad, is a shy, unassertive, and airheaded girl that doesn't have much presence in school. Chitanda Eru, the lead
The main protagonist in both animes are somewhat similar. Even thou i Hyouka the main character seems to be smarter and in Clannad more friendly, i found some similarities with both titles. Both involves the girl in which they fall in love and get out of their daily routine, they wanna change just for that person. In both animes they wanna open up lost club again.