"TK78" is a mysterious character who speaks in semi-nonsensical English quoted from pop culture depending on the situation of the scene. He saves the team many times and does know some Japanese but rarely speaks it, and it seems he understands what the others say to him. And he is talented in almost anything (mostly in dancing). He was always seen dancing even though fighting his enemies. His real identity and his name are unknown to characters in the show, even to the SSS, so they identify him as "TK", a nickname he gave himself. However behind character names in the opening sequence their Romaji name can be seen written in faint letters, and behind "TK" it says "Thei Kai".
One particular trait of his is his inability to remain still, as he is in constant movement whenever he is not doing anything at all (although at times he can be seen not in constant movement). Also, his catchphrases appear to be 'Just a wild heaven' and 'kiss you'.
He is a tall young man with blond hair. Not having the SSS uniform, he has a large dark-red bandanna that practically hides his eyes (Shown for a brief instance in Episode 10 during the 5 on 1 soccer match against Yui). He has also two small earrings on the sides of both his ears and a "necklace" that holds of a pair of handcuffs.
Throughout the series, TK has said these in English:
|1||C'mon, let's dance!|
|Okay... don't be afraid.|
|Feel the groove, man.|
|Yeah, nice and slow.|
|Music is the test|
|Mmm, this is so delicious.|
|Yeah, step on.|
|Get your little kiss|
|2||Alright let's go|
|Just wild heaven|
|Hurry up! (after that, he said: "You can make it! Oh, run to her and hug her tight!" in Japanese)|
|Give my love to jesus man (while he was holding the fallin roof)|
|3||Get chance and luck|
|4||Crazy baby (When Yui accidentally strangles herself.)|
|Don't stop dancing|
|6||Ouch, are you serious?|
|Just a wild heaven|
|I'll be back|
|7||One, two, here we go. Let's dance|
|Zetsubou no carnival|
|Crazy for you|
|Chop chop chop chop|
|8||Hey, yo! Check this out! It's a Moonwalk...It's a Moonwalk...Head-spin!|
|It's my turn. Get chance and luck|
|10||I kiss you!|
|Don't let me cry|
|In the mountain|
|Here we- (He would have said "go" had Otonashi not tackled him.)|
|Easy come, easy go|
|Scrambled it trouble down|
|11||I kiss you!|
|Woah! Dancing in the shadow!|
|like an invitation to the crazy carnival|
|12||Come on Come on Come on Come on Come on! Knockin' on heaven's door|
|Goodbye Wild Heaven|
|Extra Episode||I'm TK! I'm going my way!
That's easy, yeah. C'mon and dance, right now everybody dance easy, alright, alright, let's dance, follow me ha-ha-ha, yeah, that' right. That's an easy task.
Woo! ... Sexy-sexy baby. Sexy!
Dive into your body!
|Crazy night with Mabo Tofu|
|Mabo Tofu give me back!, woohoooo!|
|Second OVA||"Smells good"|
Most of these catchphrases are actual lines of songs, mostly from bands TM Network and B'z, rock bands from the late '80s to the present.
- Though fully capable in unarmed combat as shown in episode 12, TK uses a mismatched pair of a L.A.R. Grizzly and a Browning Hi-Power as his dual sidearms. When heavier firepower is called for, TK calls on a PP-19 Bizon submachine gun.
- In Episode 11, at about 19:43, he is shown to be dancing the moves of Michael Jackson, with the moonlight as the spotlight.
- He has taught Matsushita some dance moves.
- He is seen dancing while fighting the shadows in episode 12.
- It seems that he doesn't tire out after moving or dancing.
- The word "THI-KEI" appears behind TK's name in the opening which is likely the phonetically spelling "TK".
- He actually isn't very fluent in English, as stated by Hinata in Episode 9, despite the fact that he speaks it.
- In the Third Drama CD, Otonashi stated that without his bandana, he was a handsome, double-lidded person.
- Along with Matsushita, TK has a cameo appearance in episode 7 of the anime Charlotte.
- In Angel Beats! OVA 2 (Hell's kitchen) TK says to Ooyama "Hey, you!" in English, then in Japanese says, "Right now, she's waiting at the airport lobby," which could be a possible hint of his past. (Either his or Ooyama's)
- In writing and copy editing, "to come" commonly abbreviated to "TK". It is used to signify that additional material will be added at a later date.