Kizuna

Kizuna: Bonds of Love (絆 KIZUNA～恋のから騒ぎ～, Kizuna: Koi no Kara Sawagi?) is a yaoi manga, authored by Kazuma Kodaka. Released in 1994 and ending with the release of the final volume in 2008, it allegedly was one of the first and most popular manga to feature a homosexual relationship. It also spawned 3 OAV.

The story centers on the relationship between Kei Enjouji, a Tall, Dark and Snarky highschool student, and Ranmaru Samejima, a Heir to the Dojo. Enjouji fell for Ranmaru almost at first sight when they were kids and he saw Ranmaru practising his kendo moves, and started pursuing a relationship with him. Ranmaru is at first reluctant, but Enjouji perseveres and they become boyfriends anyway.

However, their relationship won't be an easy one... since after Enjouji's mother Hotaru dies, she leaves him a letter revealing his heritage. Which happens to be linked to a pòwerful Yakuza clan, whose leader Takeshi Sagano is Enjouji's long lost father. Enjouji and Ranmaru attempt to keep up with their lives and go to college peacefully, but the Yakuza won't leave them alone, and specially not when Enjouji's half-brother Kai takes an interest in Ranmaru himself...

Provides examples of:

 * Anguished Declaration of Love: Enjouji is good at these. Ranmaru far less so although he still has a stab at it once or twice.
 * Aw, Look -- They Really Do Love Each Other: any couple will get this at least once, and Ranmaru and Enjouji have half their relationship running on it.
 * Badass in a Nice Suit: It's smartly dressed Yakuza and assassins. What do you think?
 * Berserk Button: if you injure Enjouji, do not be in the vicinity of Ranmaru with a stick-like object.
 * Big No: Enjouji, when
 * Bodyguard Crush:
 * Butt Monkey: If something funny or humiliating's gonna happen, Enjouji is likely to be on the receiving end. Unless we count the
 * Career Killer: Roy and J.B. The guns and kill-people-for-money thing gives it away.
 * Cast Full of Pretty Boys: lampshaded by the mangaka in volume 6 "Kizuna VI... the manga which has completely ignored the existence of women!!"
 * Casual Danger Dialog: Roy is physically incapable of not doing this. Even when there's no one else around! Oh yes, he knows what he's doing but when he misses being blown up by about two seconds could he not laugh???
 * Cheshire Cat Grin: Enjouji's adopted one when he was a kid and it doesn't seem to be going away any time soon.
 * Cool Big Sis: Ranmaru's sister Yuki
 * And Rena. Er... kind of.
 * Consummate Professional: both in the Yakuza world, and that of professional killers. Roy tends to have issues with people who treat him like a rookie.
 * Crazy Jealous Guy: Ranmaru acts like this a bit about Enjouji, but it's nowhere near the serious extent to which Enjouji acts around Ranmaru. Apparently it's In the Blood because Kai acts the same way around Masa. Then of course, there's Jack, who will kill you if you sleep with Roy. No, literally. He will take a sniper gun and put a bullet through your brain if you fuck his boyfriend.
 * Determinator: Ranmaru. Kai also seems to learn this from him.
 * The Dragon: Masanori Araki, to Takeshi Sagano. So much that he's been handpicked as Takeshi's succesor.
 * Even the Guys Want Him: Ranmaru. Repeatedly, to the point where even his kendo club members tend to have a thing for him. Even guys trying to kill him seem to have enough time to remark on how hot he is. Although really, it's not like you could blame them.
 * Facing the Bullets One-Liner: Roy (yet again), and Enouji, when the need arises. Both of them also tend to use Gallows Humor, none of which their partners find funny.
 * First-Name Basis: the principal couple, Enouji Kei (extroverted, casual) and Samejima Ranmaru (introverted, formal), normally call each other "Enjouji" and "Ran-chan". When Enjouji's half-brother Sagano Kai, Samejima in confusion and anguish calls him "Kei." Told about it later by Sagano, Enjouji realizes how badly Samejima was affected because "He only calls me Kei when he really needs me by his side."
 * Heir to the Dojo: Ranmaru
 * Heroic Bastard: Kei Enjouji, who didn't know for a long time and was not thrilled when he learnt about it.
 * Heroic Sacrifice: Ranmaru in the form of a Diving Save.
 * Hitman with a Heart: Jack has a soft spot for innocent kids... and Roy. Falls into The Atoner category in that he donates money to charities and orphanages as a way to atone for his career. He tends to be very much on the side of Never Hurt an Innocent. Roy, on the other hand is more of the persuasion that If The Innocent Was Stupid Enough To Get Involved, It's Their Own Damn Fault.
 * Hot-Blooded: Kai and Ranmaru.
 * Ill Girl: Hotaru, Enjouji's single mother, had respiratory problems that ultimately killed her.
 * Ignored Enemy: if the enemy isn't worth their attention neither the Yakuza nor the hitmen will give them a second thought. If its Roy, he'll probably continue on a conversation like they're not even there. Although he does that anyway.
 * I Want My Beloved to Be Happy: Given the slightest provocation, Ranmaru will start worrying that he's a burden to Enjouji or his being with him is interfering with his ability to be happy, and will - somewhat stupidly - consequently try to distance himself or provide Enjouji with the opportunity to break up with him.
 * Gayngst: Yakuza style, and HOW.
 * Get a Hold of Yourself, Man!: Kai has to slap Ranmaru to get him to pull himself together when he sees Enjyoji has been shot. Considering his Berserk Button and the fact that Kai left a sword in his vicinity, this may not have been the best idea.
 * Green-Eyed Monster: The Envy Kai has towards Enjouji drives a good part of their conflict.
 * He also gets terribly jealous and threatened when he thinks Enjouji might be cheating on him.
 * Last-Minute Hookup: Kai and Masa manage to narrowly avoid this trope by being technically together for a couple of volumes, but they finally had sex in literally the last 20 pages. Anyone want to know how many volumes were leading up to that point? Here's a hint:
 * Loveable Rogue: Roy. Even Kai can't help but like him eventually - no matter how many times he threatens to move in on Masa. Enjouji also has a fair bit of this in him, particularly around his highschool years, but he never fully fits the trope as well as Roy does, and he outgrows it by the time he and Ranmaru are essentially married. Well... almost.
 * May-December Romance: Masa was - apparently - in his mid to late teens when Kai was born. He spends the majority of Kai's childhood acting like his big brother... which is why he has more than a few issues with how he feels about him later on. Kai, otoh, doesn't see the problem.
 * Missing Mom: Hotaru's death is in fact a huge plot point.
 * Names to Know in Anime: The OAV series has a top-notch voice cast: Ryotaro Okiayu (Ranmaru), Keiji Fujiwara (Kei), Ryo Horikawa (Kai), Akio Ohtsuka (Masa), Akiko Hiramatsu (Yuki).
 * The Other Darrin: In the second OAV series, Kazuya Ichijou replaces Keiji Fujiwara as Kei.
 * Noble Demon: Jack, especially around Roy. The reason he initially leaves him is because he doesn't want him to follow in his footsteps to become a killer. Not that that helped any.
 * Non Linear Story: No, you did not miss four books between chapter 1 and chapter 2. Yes, you are going to have to pay really close attention to things like uniforms, scars and hair-cuts if you want to try to figure out which stories and chapters go where in the overall storyline. No, the chapters that interrupt story arcs haven't been accidentally put in the wrong place. And yes, expect multiple character origins told after they've been introduced for a couple of volumes. For anyone who gets lost, Kei's long hair and Masa's scar are good temporal landmarks.
 * Out-of-Genre Experience: you remember that chapter with the angels? Yeah. They have pretty wings though.
 * Parental Substitute: Masa practically raised Kai.
 * Redheaded Hero: Ranmaru
 * Red Oni, Blue Oni: Kei and Ranmaru respectively, especially in the beginning of their relationship, where Ranmaru was continuously cold and reserved while Kei was the one pursuing him with impassioned declarations of love.
 * Retired Badass: a strange example in Ranmaru, who was forced to quit kendo after he . But that doesn't mean that if you piss him off enough he won't kick your ass into next week.
 * Rescue Romance: What truly set off Ranmaru and Enjouji's romance was
 * It should be noted that although they already had a fully established and loving relationship beforehand,  completely changed the game and forced their relationship through the make-or-break hurdles.
 * Slap Slap Kiss: Ranmaru and Kei's relationship has a lot of this, even though it's nearly always followed by Aw, Look -- They Really Do Love Each Other moments. That said, Enjouji can occasionally take it too far and take a swipe at Ranmaru through his insecurities about their relationship that actually hurts him - cue him regretting being a Jerkass and trying to make it up to him.
 * Spoiled Brat: Kai, at the beginning. He gets better.
 * Tall, Dark and Snarky: Enjouji.
 * The One That Got Away: variations on this are all through the series. Even Ranmaru and Enjouji's relationship has traces of this. However, the only couple that play this without variation is Jack and Roy - followed by standard New Old Flame.
 * This Is Gonna Suck: Roy. It fits in with his Casual Danger Dialog compulsion.
 * Tsundere: Ranmaru. Holy shit, Ranmaru. He's - generally - a type B though: nice and kind, but EXPLODES with the force of a bomb when he gets pissed.
 * Kai on the other hand is a type A through and through... unfortunately for Masa.
 * What the Hell, Hero?: Ranmaru slaps Kai and verbally beats him
 * Yakuza: Very involved in the storyline, due to Enjouji being the illegitimate son of a Yakuza boss.
 * Yakuza Princess: Genderflipped with Enjouji's half-brother Kai Sagano. And possibly deconstructed, since being this screwed him up pretty bad.
 * Yaoi: A staple of Yaoi series.
 * Yakuza Princess: Genderflipped with Enjouji's half-brother Kai Sagano. And possibly deconstructed, since being this screwed him up pretty bad.
 * Yaoi: A staple of Yaoi series.