Is Japan Embassy Homophobic?

I’m planning to apply for a Japan visa this year, and it will be my first time traveling there. I was advised to include who I’m traveling with in my cover letter to make my application stronger, especially since I’m self-employed as a musician. I’ll be traveling with my boyfriend, who has previously visited Japan, so I’m wondering how I should indicate our relationship in my cover letter. Since we’re a gay couple, I’m also wondering if it’s risky to disclose that he’s my boyfriend, as I’m not sure how LGBTQ-friendly Japan embassy is. Any mature advice?