The Ace: He pretty much excels in every studies in the school, even downright to answering a question for high-schoolers under a minute. Then again, it makes sense considering how he has been into one loop and remember the other.
Broken Ace: However, he does have personal issues. See Broken Bird below.
Adorkable: No, really. Once he opens up, he pretty much becomes one of the most adorable and by far the dorkiest character from Next Generation.
Aloof Ally: At first. He eventually becomes one of Roku's True Companions later on.
Alternate Universe: He comes from one.
Badass In Distress: During the first arc in the third season of Next Generation.
Because You Were Nice To Me: Kakeru is only nice towards Roku because he was willing to be his friend.
Beneath The Mask
Berserk Button: If you try to hurt Roku or his mother in any way, he will drop his cool and beheads you.
Big Brother Instinct: Towards Alice and probably to Oz as well.
Big Damn Heroes
Blessed With Suck: He's the current Twilight Key holder, however, he considered the power something more of a curse. Then again makes sense who's his father was before..
HIs time powers also makes him remembering the events on the "real" world's time loops (courtesy of Mary), which is one of the reason why Kakeru's not bothered by how Hayato acts.
Break The Cutie
Broken Bird: Due to being the Twilight Key's holder, Kakeru's life in the Alternate World pretty much broke him to the point of him being almost an emotionless and apathetic person.
Brutal Honesty: He freely tells Roku that he's a naive idiot. He's even harsher on other characters, particularly to Shintaro and Mary.
But Now, I Must Go: At the end of both Next Generation and Revenant Night.
Archer Archetype: Fills the character archetype nicely. He works on his own, not relying on anyone and is very aloof. He gets to use a black bow later on after the Gabriel arc.
Cool Sword: He has one used for his Weapon Meister ability.
Casting A Shadow
Time Master: His Arc of Time Magic.
Fusion Dance: Junction does this with Oz.
Healing Hands: One of the Twilight Key's power is to able to "restore" anything the user touches.
Healing Factor: It also instantly heals the injuries inflicted on Kakeru.
Reality Warper: His "Twilight Key" Ability allows him to be one.
Sinister Scythe: His main Weapon Meister weapon.
Swiss-Army Weapon: With Weapon Meister, Kakeru is capable to transform his sword into either a scythe or a bow.
Time Stand Still
The Comically Serious
Conditioned To Accept Horror: What his world has done to him. This would explain why Kakeru never felt any grief seeing people died, since he already saw a lot in the "Alternate World" at least with the exception for Roku's father, Ruki.
His Arc of Time also responsible for this too. Since most of the memories he sees in the "real" world are at least Mary's fault for resetting it too many times.
His Arc of Time magic allows him to control time, wether stopping it, or traveling backwards to it, he retains his memories, which is why he knows a lot of school subjects, and a lot about Roku even though they've never met before.
How did Kakeru managed to incapacitate Oz? He deliberately missed on him, as the arrows near Oz are magic-enhanced paralyzing arrows which were activated after Oz makes his first move on Kakeru.
Dangerously Genre Savvy: As a result of a lot of Mental Time Travel.
Dark And Troubled Past: He's the holder of the Twilight Key in the Alternate Universe and was practically targeted by the Ainsworth House for years.
Defrosting Ice King: Starts off as a full-blown Ice King due to having Seen It All several times. However, as the series expanded, he becomes more defrosted and practically turned into one of Roku's True Companions.
Deuteragonist: Of Next Generation.
Eerie Pale-Skinned Brunette
Emotionless Boy: The "emorionally repressed" type due to all the trauma he's seen, not only his past but also Mary's fault. Eventually unrepressed near the end of Riddle arc.
Expy: Has a similar personality and powers with Homura from Puella Magi while his backstory is closely resembles Miyu from Fate'/'Kaleid Liner Prisma Illy'a.
Full-Named Basis: For most of the series and towards most people, with the exception of Roku and Keith, at least for the latter at times.
He's Back: Comes back during the third season of Revenant Night.
Heroic BSOD: He comes closed to this during the Gabriel arc after realizing he'll die anyway, only Roku's interference snaps him out.
He also has one again during the Ainsworth arc, after he gives up believing Roku will come save him, and yet again, Roku is the only person that can snaps out Kakeru.
Hidden Heart of Gold: While Kakeru is mostly nice towards Roku, he does show that he does care for everyone's wellbeing, mostly with Alice. Given how he act towards her is the same as he does to everyone other than Roku, it's quite sweet how Kakeru appreciates Alice as his Arcane and friend and even says "I like you" to Alice to cheer her up.
Ho Yay: Has a lot of these with Roku. Not only that, even one of his Arcane, Oz is pretty much attracted to him.
Identical Stranger: Mukuro mentioned that Kakeru slightly resembles Satoshi. Even Sora mistakes Kakeru for him once.
If It's You, It's Okay: To Roku.
I Gave My Word: He keeps Ansem's (who he dislikes of) promise to not hurt Shiki when they fight.
Macguffin Guy: He's the current Twilight Key holder. Hence why he was taken to the "real" world, so he would be safe from the Ainsworths that were targeting him.
Mismatched Eyes: Has a red right eye and a gold left eye, which the latter was caused due to having him implanted the "Twilight Key" by Ansem.
New Transfer Student
Nice Job, Breaking It Hero
Not So Different: Despite they're personal differences, Kakeru is this with Keith. Given how they're the Chosen Ones of their world with troubled past and issues with family, it's no wonder Kakeru admits that Keith's life must be suck.
Oblivious To Love: He does not realized that Alice has quite a huge crush on him, since he viewed her as a friend and a little sister to him.