In Black Cat, there are many many moments of Ho Yay between Creed and Train. Creed getting incredibly aroused by Train killing, praising Train's body and beauty like crazy (much to Train's discomfort), constantly offering We Can Rule Together speeches to Train because, according to him, his entire plot to rule the world will always be incomplete if Train isn't by his side as his Queen partner, playing some elaborate sounding songs rather passionately on the piano while waiting for Train ("It's almost finished Train, the composition of homicide and friendship we shall play together...But I want more of a furious/intense melody, and one that is sensual as well."), constantly thinking/talking about Train, killing off a bodyguard that "put a mark on Train's beautiful face," sneaking a letter into Train's room that's enclosed with a rose, going off on a murderous rage against anyone who badmouths/threatens Train or who "tries to come between me and Train", acting like he was dumped when Train chose to save his friends instead of fight him, out-and-out stalking Train by using Shiki's insects as spy cameras to watch Train sleep, and even moaning and daydreaming about Train while naked in a rose bath. In a fight scene during episode 5, Creed goes into fanboy mode while fighting Train praising his skills/abilities (english dub) "Train you are the ultimate! Such talent...you are...FLAWLESS! Your moves are...incredible...this spar with you is one of my life's dreams...I've always wanted to taste a spec of your power!", (japanese sub) "Your skill never ceases to amaze me, Train. Your nimble body and dexterous gun-wielding skills, it's marvelous! You're wonderful, just wonderful! I always wanted to fight you like this once. In order to feel your potential." Then Train gets into a...rather compromising position on top of Creed with Creed sounding like he had an orgasm (getting really excited and breathless) when Train defeated him by smashing his gun with Creed's sword, breaking it in half, complete with Creed's creepy (in the japanese version) "Ah, Train. You are the best...To be able to break my Kotetsu with your orichalcon Hades. I reaffirm the fact that I need you. I can envision it clearly. The door to tomorrow, the bright future that's meant for both of us!" and (in the english version) "That's it... my Heartnet...you are greatness, true and pure...snapping my Kotetsu like a twig with your Hades...it's shocking! It's power that I need...It's there...the door...to tomorrow...a bright future...a future with you! Can't you see the glory?! Can't you see what a wonderful day this is?!" with tears in his eyes. In response, Train just looks at him disgusted, gets up and leaves with "Creed, I don't ever want to see your face again" and walks away. Creed just lays there for a bit before getting up and gazes after Train longingly while thinking "Train..."
Following that, when some men from Chronos show up to mock Creed about how even he couldn't capture Train Creed goes off on a insane rage against them, killing them before gazing back at the direction Train had gone while saying "And I was in such a good mood until you three showed up...I don't have time for you...All I see is Train...Only Train..."
And in the manga Creed actually says "All I want...Is Train's heart!"
Creed (To Sephiria): "I'm in the middle of an important discussion with Train. If you insist on interfering...the price will be death." And then Creed pretty much leans in close to Train to whisper in his ear "Train, let's make a blood festival out of her together."
And before Train and Creed's "reunion" Creed broadcasts videos of himself all over the city in an attempt to get Train to come to him. One of his lines is "Ever since I heard you were in town my heart has been quivering." And when they finally meet Creed comes out with a rather questionable line "Now it is time for you and me too..." before he is cut off by a bullet from Train who asks him why he killed Saya. Creed is shown getting very excited at the look in Train's eyes "Yes! Those eyes, those are the eyes!" Then Sven shows up and the look on Creed's face is priceless "And who are you? Are you going to interfere with the reunion between Train and me?!" And later still he says to Train "I'm content at just being able to see your face today. I'm not going to give up. You will definitely come to my side."
And later Creed spies on Train talking with Saya and is shown getting insanely jealous, crushing a rose in his hand and saying with a look of pure rage on his face "What?! Who is that girl?! She's poisoning my Train with her words/What are you telling my precious Train?! You Goddamn witch!" Interestingly enough, the only times Creed has ever been shown to cry have been when Train is concerned. And Creed becomes very embittered and horribly jealous that his numerous attempts to have Train join him to rule the world fail because of Saya's influence, so he eventually decides that he would rather that Train die than remain under the spell of "that witch," even telling Train that he would at least want to have Train by his side even as a dead body rather than let Saya have him. In one instance, acting very much like a Yandere, Creed even tells Train (after he smashes Train into a wall): "This is all your fault, Train! It's your fault for making me mad! Time and time again, I come to get your cooperation so it wouldn't come to this. But despite that... all those attempts were futile. All of them!"
In regards to Saya, Creed murdered her when Train started developing a deep friendship with her. And when that didn't manage to convince Train to come to him, Creed decided that it is now Sven's fault, including getting jealous of Sven's strong Heterosexual Life Partnership with Train and trying to turn Sven into a monster so Train will join up with him instead. And later trying to kill Sven, but, of course, he ended up failing in that tactic.
Though it's rather one-sided, as Train clearly has zero intention of returning Creed's affections. However, despite Train's loathing for Creed, he once rescued him from falling off a rooftop at the risk of his own life, and despite the fact that Creed killed Saya, Train refrains from killing Creed at the end and lets him live, deciding that, along with him, Creed must live a life of repentance.
And later in episode 20, we find out that Creed had made a gigantic mural of him and Train together and a life-sized sculpture of Train.
As well as his obsession with Train's beautiful eyes. In episode 20, Creed, rather dramatically, throws purple paint over the picture of Train saying with much disappointment "I wanted to at least paint the eyes of this picture red with your...No, our blood...and finish it. But in your present state, red doesn't suit this image. After all, a beautiful crimson hue wouldn't fit someone who has lost their killer instinct" and destroys the sculpture of Train while saying "This sculpture would have been complete if I engraved the menacing presence in your eyes."
Then there's Echidna's love for Creed, but Creed is too gay for Train to care and in the anime, it is shown that she notices Creed's unhealthy obsession with Train, and therefore harbors deep resentment towards Train.
Creed even begs (in a very perverted way) for Train to shoot him in the head, that he will take any bullet he has because, in Creed's words "once I have taken it you and I will be bonded forever." Also, the fact that even though Train tries to beat it into Creed that he is not interested in him, Creed is shown to really enjoy it when Train attacks him and just can't take a hint that Train hates him.
Not to mention how the official translation of the manga has Train call his partner Sven "Svenny-baby", especially when he knows Sven is upset with him.
Heck, everything about Sven and Train's relationship is suspicious. This is lampshaded in the anime, where a waitress notes that Sven is the father, Eve is the daughter, and... awkwardly skips over Train. This is only made further blaring by Creed's insane jealousy of Sven (which culminates in a bigMurder the Hypotenuse moment - "if I get rid of you... then Train will come to me!"), which was most definitely justified considering how coy and playful Train acts with Svenny-Baby.
Then there's Eve's crush on Sven, and how Sven is much more concerned with Train (being Train's "partner" and all). Interestingly, she finds Train's relationship with Sven enough of a threat to be jealous of Train.
And during Train and Creed's reunion, Sven shows up to help, making Creed extremely jealous, and Durham points his gun at Train. Sven takes the bullet meant for Train, letting it graze his shoulder.
Another moment in the manga is when Creed is about to shoot Sven with a nanotech "Lucifer" bullet, and Train takes the bullet for Sven in his arm. Train promptly punches Creed. Hard.