Hello, thanks for playing! Are you in New Game+ mode? Endings/epilogues are only available in NG+, and his is always available. The only way to miss it is if you're choosing too many of the options that make you too envious/bitter towards him as you'll automatically think better of reaching out to him when selecting his name. There is also a choice guide you can toggle on in the preferences menu that will tell you what your choices are changing.