Kinji certainly fulfills his role as the Unlucky Everydude and Deadpan Snarker. His quips (especially in the light novels) can give even Kyon a run for his money!
Any time Shirayuki, the Unlucky Childhood Friend Miko, misunderstands nearly anything that Kinji and Aria do together. And by 'any time', we mean 'all the time'. Kinji being Aria's partner doesn't help matters.
Shirayuki provides a lot of golden moments, for that matter. You see your crush naked? Shirayuki's solution: Take off your clothes too. You see another girl with your crush? Shirayuki's solution: Bring out your katana.
That one incident with Shirayuki and Aria after the first 'Butei Killer' arc. Shirayuki learns that Aria and Kinji shared their first kiss and nearly goes batshit insane. Aside from blushing, Aria's response? "D-Don't worry, I-I d-didn't get pregnant!" Turns out Aria thinks getting kissed on the lips turns you pregnant. Cue Facepalm from Kinji and Shirayuki fainting.
In the light novels Kinji adds his own snarky line. Along the lines of, "What the hell, Holmes family? You didn't even teach your great-granddaughter sex-ed or something?"
And the following morning. Oh Aria, haven't you learned from Shana that asking how babies are made never turns out well? And reading a book with DIAGRAMS doesn't help much either...
A definite Crowning Moment of Funny is the end of Volume 5. In a casual and nonchalant manner, Reki proposes (as in, a marriage proposal) to Kinji, WITH her signature rifle POINTED AT HIM! Naturally, Kinji freaks out.
A funny moment for this troper is also at the beginning of Volume 6 where Reki gives Kinji a challenge: If Kinji can avoid being hit for more than a minute by Reki's seven attacks, she will retract her proposal. And this is coming from the girl with Improbable Aiming Skills of a 2051 meter range.
Most moments involving Riko are this. Her The Tease moments with Kinji are quite hilarious.
Jeanne d'Arc, The Ojou and The Ace Expy of Saber, is good at almost everything. 'Almost' because Kinji finds out that Jeanne's drawing is about as good as an elementary school student's.
What about Kinji meeting the Mission Control and Jeanne's best friend Misaki Nakasorachi in person? No wonder the girl's only Rank B. Misaki can't converse with people in person, instead she prefers to talk with them through a device because of her extreme Shrinking Violet tendencies.
The first half of Volume 8 contains pretty funny moments, such as: Kinji finding out the hard way that one of his allies, a fox girl named Tamamo, wears no undergarments, or an eighteen year old nun who drinks strong liquor inside his house and believes that his older brother (who is a Wholesome Crossdresser) is actually a girl.
How about the following morning? Aria wakes up in Kinji's room, just the two of them. Seeing the bottles of liquor on the floor, plus a bite mark on her neck (actually a bite from Vlad's daughter Hilda) and a blanket covering her body, Aria goes completely batshit insane on Kinji, believing that he used alcohol so he can do weird things to her. Meanwhile, Kinji is completely oblivious on why she's acting so embarrassed and angry.
Kinji, wondering what Reki is listening to on her headphones, lifted the headphones off her head. Reki's response? Play 'Firestarter' by The Prodigy at a high volume and turn it up to max, making Kinji nearly go deaf. Seems like Reki doesn't like her headphones being taken off.
And their class Cosplay cafe (also in Volume 8) for the school festival. They draw roles from a cardboard box and can draw twice if they don't like their first draw, but the second draw is absolute. During Aria's turn to draw, she draws first 'Idol'. Aria is close to tears, and Riko, Shirayuki, and even Kinji are stifling chuckles. Aria decides to draw again and what does she get? To quote the light novels:
Riko, who shouted that, was rolling around at the feet of Aria, who was restraining herself like she had been frozen solid at the moment she saw the three words, "Elementary School Student", and laughing uncontrollably, she clutched her stomach.
Was it that Shirayuki had also reached her limit of tolerance? She had knelt down as if prostrating herself, and leaking a noise of laughter which could not be called a voice, she hit the floor with a thudding noise.
I, who stood there shocked at the depths of horror in which Aria's luck resided, also - unintentionally - thought about a elementary school student with sharp eyes, sucking on a lollipop and carrying a red backpack— I laughed, and at that moment, I noticed the killing intent of Aria, who seemed to have snapped.
In the middle of my brain, the high-impact song "Firestarter" once again started to stream.