The actors are very experienced and are able to convey their thoughts and feelings in a realistic and believable fashion.
This gay couple in their 40's, at first, seemed mismatched and in one internal dialogue Shiro has he admits Kenji would not normally be someone he is attracted to but for a life partner he is his ideal. The internal dialogues are scattered through the episodes and give further insight to their relationship.
Like most couples (they have been together for around 3 years), there are some doubts and insecurities that help us, the audience, to appreciate the extra societal restrictions, as a gay couple, they have to navigate.
A very telling scene towards the end is when Kenji explains to Shiro's father the career options faced by men when they realise they are gay and will not be marrying and having children. It is very poignant.
The every day actions of work, domesticity, shopping and cooking that this couple share demonstrate the love and care they feel for each other. Other gay couples are introduced and highlight different aspects of how Shiro and Kenji relate to each other. Shiro's respect and diffidence towards his parents and their gradual opening up to how his sexual orientation will impact their future is handled sensitively.

So excited to find there is a follow up movie of the same name - now on my PTW list