@299792458
Ah, that's an interesting reason for the paintball being there. I thought it was odd that Eba brought the paintball, especially since he wasn't aware that Fukurou was going to be there to begin with. I was thinking instead that it was Usogui who did something, perhaps he had one of his men come in immediately after receiving the call about the match to save him.
The whole situation kind of reminds me of when Baku had Kaji try to lose his first gamble, in order to help him gain experience. At that time, Baku had GPS on him and was keeping watch him, and also armed him with Marco. Was that degree of setup inspired because of his failure to save Hal in the past? Or did he actually have that much preparation back then, and was actually keeping an eye on Hal? Maybe Baku knew that Hal would be pushed into wanting to prove himself as a gambler, and intended for him to lose and gain experience, but didn't intend for him to forget everything due to the sudden memory loss? I'm personally leaning towards the idea that Baku was intentionally pushing Hal to gamble, but made a mistake and lost him, and that's why he felt guilty when talking about the memory to Yukiide.
If it was indeed Eba's help, and if your speculation about Fukurou playing Russian roulette often is correct, then back in the Tower of Karma match, that detail probably helped Usogui realize that the Suteguma vs Fukurou match was fake, since they didn't play Russian roulette at that time.
The memory loss is indeed suspicious, I suspect it may have been induced as well, because the interval seemed to be way too short. The initial bookstore memory loss apparently happened on Nov 16, so it happened again in merely one week. One random & unlikely possibility is that Hal lost the game because he experienced a memory loss while playing, thought that would make mean he had a third memory loss, which seems unnatural & excessive unless it was induced somehow.
The way the author skipped over the Fukurou match is quite interesting. It feels like we're experiencing Hal's memory loss for ourselves, and as a result there are so many different possibilities to consider, and filling in the gaps feels quite impossible. It definitely feels like there are a lot of suspicious gaps and details, especially with Eba as you said. I think there is a lot of room for different twists here, but we don't have much evidence to work with. What a rough condition to have to live with.
Baku & Hal's relationship is quite tragic indeed. It feels especially sad in the present day, where he knows that Hal is technically alive, but is really dead. Combined with the fact that the current Hachina is super antagonistic towards him, since he knows that Baku's a Kakerou member, and that he's attempted StL, and that he owns the bookstore, and thus thinks that Baku is most likely trying to manipulate his memories.