You weren't Shinobu's tsuguko since you declined the offer and gave it on to Kanao but that didn't mean you shouldn't know of Shinobu's plan

She purposely waited a year to tell you she was injecting poison into her body just so she could be sure you wouldn't do something stupid. You questioned her of why you weren't in this plan and she came out with a brutally honest response

"Nowhere, obviously. You are too weak to engage with a Lower Moon and come out alive, much less an Upper Moon."