So, the blonde man in chapter 5, "Hisashi" was previously adopted by a yakuza man called "Nishijima", hence he has his surname in the later timeline. Before working in the shop, and being a sex worker, he used to be the No.1 host of a club, which was the timeline of the adoption. So when Hisashi refers to his deceased partner, he is referring to Nashijima. Nashijima also wanted Hisashi to stop being a host.
I never noticed this until now... this makes me so sad for hisashi and nishijima-san. From the little bits we see, they seem to be so in love with each other.
So, the blonde man in chapter 5, "Hisashi" was previously adopted by a yakuza man called "Nishijima", hence he has his surname in the later timeline. Before working in the shop, and being a sex worker, he used to be the No.1 host of a club, which was the timeline of the adoption. So when Hisashi refers to his deceased partner, he is referring to Nashijima. Nashijima also wanted Hisashi to stop being a host.