It's implied in one episode that one of the reasons Kougami makes so many cakes is to make sure if an employee in his company has a birthday that day there'll be a cake ready.
In episode twelve, the Yummy's host is a friend of Eiji's that he met while abroad. His desire is to be famous, and the Yummy is stealing 'talent' from others and sending it to him, warping his personality. He eventually hows up at the cafe demanding that Eiji let him use his experiences as his own; Hina is horrified, but Eji says he doesn't care about that and just wants his friend to go back to being himself. Then Ankh pulls Eiji aside and says he should go take out the Yummy, because it's 'probably built up a lot [of medals] by now,' but the entire exchange comes off as him trying to reassure Eiji that he has the means to save his friend...
In episode sixteen, there's a small moment when Eiji is having a realisation about how much it must suck to be a Greeed, and looks at the destruction wrought by Mezool's loss of control. Not only does he express sympathy for her and Gamel, but he also makes a promise about Ankh, that the Bird Greeed doesn't seem to hear; one that makes it pretty that, for all their arguing, Eiji has started to care for the jerk.
Eiji: 'No. I won't let this happen to you.'
The 1000th episode Homage arc in #27-28. A plotline of any sort would normally seem like an afterthought for a storyline condemned to Bottle Episode status, but not only is continuity left intact, but the story even ends with the image of a ShockerMook and a Kamen Rider shaking hands and making peace. For a 1000th episode, this was very long in coming indeed.
No mention of Date desperately wanting to continue making the Kamen Rider film even after getting injured?
Ankh: You want your paycheck that badly?
Date: No! A movie is the realization of a dream! And it can inspire a whole generation of children to dream too! What more could I ask for my work?
Kougami: That's the indomitable spirit of filmmaking!
In #32, after Eiji ends up badly beaten by the first two Dinosaur Yummy, Ankh asks him if he's alright. Counts because this is the first time Ankh seemed to actually show true concern for someone other than himself.
Even before this, examining Ankh's behaviour even in a few of the early episodes, it's possible to see his attitude as morphing into something like This Is My Human towards Eiji—sure, there's probably a degree of self-interest in there (it is Ankh, after all), but he comes across as legitimately concerned at times; like trying to stop Eiji from doing combos too much because of the strain it puts on him. Ankh really wants to stay a Jerkass, but in some good story telling, you can tell that Eiji's general likability has been creeping up on him for a while.
In #38, before Gotou going all Tranquil Fury on Greeed ass, in order to avenge Date's "death", Date's "dying moments" along with Gotou crying out his name was pretty heartwarming.
In #40, Ankh discovering he can't bring himself to hurt Hina and Eiji anymore, followed by them throwing him a birthday party (well, technically it was originally for his host, but Hina changes her mind), which by the end he actually seems to enjoy. Considering it's probably the first time in his life anyone has ever done something like that for him, it's really touching. However, it only makes what happens afterwards all that more tragic...
It may just be me but the whole fight between Ankh and Eiji was one. Both still are bonded to the other, and this is shown at the end, where Ankh asks Eiji if he's ever really really wanted anything...which ilicts this exchange.
Eiji: "I wanted...there was something I wanted once, but...I gave up on it... I tried to focus on what was in front of me... The power to help people, no matter how far off they are! More and more! And then... I got it. You gave it to me. I never mentioned that did I? Ankh. Thank you."
The look Ankh gives while Eiji's speaking as well as when he's finished, tells the story.
#47. Where do we begin? Ankh's Heel–Face Turn resulting from the discovering that he's too attached to Eiji to kill him. Chiyoko finally being let in on the whole thing and telling Hina she shouldn't choose between any of those she cares about and should try to save them all. This leads to her going to Ankh and asking if he's all right, something Ankh at first thinks is about his body and is surprised that Hina genuinely cares for him. This leads to Ankh going back to help Eiji in the Final Battle despite the fact he's sure his Core is about to shatter and spell his demise.
The twin Births trying to talk Eiji down after he goes Greeed again during the fight with Maki
Eiji: "But I have to stop the end of the world...with my power!"
Date: "You dumbass! Take a look at your hands! What can you do with those? What are you going to protect? Who are you going to reach!?"
Goutou: "Quit trying to do everything on your own Hino!"
It doesn't work but the two continue to try regardless.
#48 had an odd one in the case of Dr. Maki giving Kiyo-chan to Chiyoko. Considering how Dr. Maki is the Big Bad, one wonders why this counts as a heart warming moment. It's mostly because of the context that lies with what Kiyo-chan and Chiyoko mean to Dr. Maki. You might want to check the fridge page for more details. Although soon after that scene, we get reminded on who Dr. Maki is at the moment.
Ankh confessing that he was happy that he was able to 'die' even though he is just a pile of medals, and telling Eiji that it was all thanks to him.
Ankh appears to both Eiji and Hina to tell them goodbye, and leading each of them to a half of his shattered Core Medal. His moment with Hina is especially fuzzy since he gives her an honest, genuine smile right before he disappears, as if to thank her for everything. Not to mention earlier in the episode he was happy that he was even able to die like a real living being, because of Hina and Eiji. Oh, and he finally admits that picking Eiji to be OOO was a good choice.
The first one to do so is Gotou, which goes to show how far their relationship has come since the two met.
In the Wonderful movie, after he and a chunk of the city are displaced into feudal Japan, Eiji is presented with a Sadistic Choice by one of Gara's proxies. Eiji will be allowed to return to the present day, but when he leaves, the village and everyone left in it will be destroyed. Uncharacteristically, he agrees to the deal on the grounds that if he doesn't, no one will be able to stop Gara. However, he will only take the deal if Hina and Ankh can go with him since they're like family to him, so Gara's proxy agrees to spare everyone he considers family. Turns out, Eiji considers everyone in the village, whether from the past or the present day, to be family, and his desire to save them all completely overloads the machine Gara had been using to gather cell medals and trigger The End of the World as We Know It.
Heartwarming points go to Kougami in this scene, too, because he was the one who suggested that Gara approach Eiji in the first place for exactly this reason.
While its place in canon is... dubious, the official video for the ending theme is a big song-and-dance including everyone from both the modern day and feudal Japan. While Eiji initially has to drag Ankh into it, by the end the Greeed is quite clearly enjoying himself!
Movie Wars Megamax has the reunion between the old gang, for one, and the story of Miharu Minato. Seeing Minato go from someone very weak and unsure of himself to a strong, confident Rider thanks to Eiji's kindness is wonderful to watch. This pays off in the third act, too, when Minato comes back and gives Eiji the Super Medals that turn the tide in the fight against the big bad.
Ankh taking the Medals from Poseidon, something Eiji can't currently do, and giving them back to Eiji, making this the second time Ankh has given Eiji the power to help people.
The revelation that the Ankh in the film is also from the future might seem sad at first since he's still gone, but as Eiji points out, this means that he's guaranteed to fix Ankh's broken medal one day.
In Let's Go Kamen Riders, The moment each Kamen Rider, from V3 to Double, appears, doubles as awesome and heartwarming, Awesome as each of the Riders appears to aid their brothers, giving off their signature pose and name, and Heartwarming to hear the crowd cheering them one by one, showing that spirit of the Kamen Riders live in everyone.