In the last episode, when Saiga and Kagura are reunited for good. Also qualifies as a Tear Jerker of the Tears of Joy kind.
Despite the fact that he's still a ruthless gangster, the fact that Niihari is collecting so much money to build a monument to his dead friends is pretty heartwarming.
Niihari: "Now that's a dream that's fucking worth something."
In fact, everything between Suitengu and his Five-Bad Band that shows just how close they are. Especially the scene in which they part ways for the last time:
Suitengu:*After giving each of his four Co-Dragons a case of gold Euros* "There are those in the government who intend to eliminate me. From this point on, the fight is between them and me alone. I can't ask you to join me. There will soon be nowhere in this country, or in the world, for that matter, where I will belong. Only Kagura and I shall remain here to face our fates. You've all worked hard for me, and have been incredibly loyal. You have my sincerest gratitude." Kikukawa:*Taking her case* "Well, boys, this is where I get off. Though it has been quite a ride." Tsujido:*As Niihari reaches for his own case* "I'm staying put. You can take my share if you want." Niihari:"You fucking serious? Tsujido, you stick around here and they'll fucking slaughter your ass." Tsujido:"What can I say, ever since we met, I've admired his scent. And regardless, I've been living on borrowed time since that day." Makabe:"You know, fuck it. Take mine too." Niihari:"Makabe?" Makabe:"Long time ago, I promised myself I wouldn't go out till I was on top, and somehow, I doubt I'm ever gonna get any higher than where I'm at now." Niihari:Aw, come on! So this is how you assholes honour Suitengu? By ignoring his last fuckin' wishes? He told us to run, right? Ain't it up to the three of us to live so we can go and tell the world all the great shit he done?" Tsujido:"Niihari, I think that's a task you were born to perform." Makabe:"We'll meet again, if the fates allow." Niihari:"Cocksuckers." *He takes two of the cases and heads for the door before turning back in tears* "Try not to get dead."