Conflicted feelings.
For once, it's a nice to see Reiji show other emotions outside of being a crybaby or being too passive, but on other hand, bad timing to unleash that repressed rage. Yuko made his, grandma, Kazu and Gen's lives hell, and doesn't deserve to die happily without watching the consequences of her manipulations first, but if Reiji actually goes for the kill, that shit would bust his chances to find Nagi.
Whatever, this definitely had to happen someday, the 1st step to close the mom-son plot before facing the final boss. And Ryou already spoiled the outcome of Reiji's actions.
On other hand, Yuko's delirium have her being already a nurse and being on her late 29s-early 30s. And she seemed to attend a 30yo Akira who was on a hospital bed (he said he did hard drugs with his 1st wife, so it could be due to an overdose). This raises the big question on when did Esemori realize he was sterile?? Because he said he found that out during his 1st marriage, but maybe he got married after havkng something with Yuko.
So, the chances of Esemori being Reiji's dad have returned maybe... or may it be a happy hallucination from Yuko. But at least this confirms Reiji's mom never stopped loving Esemori.