
Only now have I realized that Hayashida and Natsuo were in a relationship with each other before their current partners in their stories...

They weren't in a relationship. Hayashida was in a relationship with someone else called Yumi. That's who is smiling in the picture with him. You can find their story in Azami and Sabita Yoru.
http://www.mangago.zone/read-manga/azami/
http://www.mangago.zone/read-manga/sabita_yoru_demo_koi_wa_sasayaku/
Ijuuin should definitely be paired with someone but I'm hoping he gets paired with his editor (or some editor) that was also a fan
Ah!! His editor was Shizuku Ishi! The one who left the note and food for him. I was wondering who that name belonged to.