For most boys getting into the friendzone with a girl would be seen a unrecoverable failure, but for Shirashi-kun this may be the most important milestone in his life thus far..
Well you know what they say, "When life gives you lemons.."
Also Kubo-san's pout-level is increasing at a staggering rate, she was practically becoming a moe balloon by the chapter's end.
"Don't make Lemonade. Make life take the Lemons back! GET MAD! I don't want your damn lemons, what am I supposed to do with these? Demand to see life's manager! Make life rue the day it thought it could give Cave Johnson lemons! Do you know who I am? I'm the man who's gonna burn your house down! With the lemons! I'm gonna get my engineers to invent a combustible lemon that burns your house down!"
When the mc is so dense and such a loner that even getting friendzoned can be thought as progress. Even if Kubo confessed/proposed to him, this dumbo will never realize it.
Kubo, your best option is straight going for the “mother of his children” route. Play the long game.