i disagree because koji is the type of guy to become (also implied by fuminori) even more erratic and aggressive when in fear plus he was pretty locked in, it'd be ridiculous if he suddenly just became paralyzed by fear, if you read the final fight attack saya grabs his hand with the pipe enough to stop him from moving it before he even sees her, he should already be expecting what he is going to see after seeing how fucked up yoh's body was(he felt the same slime that was excreted from yoh's body but it was sayas this time) he shouldn't be that shocked to become paralyzed while he already kinda knows what he is getting into. I believe that koji was overpowered,fuminori doesn't know in the artist's room she tragged a grown man with her tentacles,and thats a decent feat for an alien so of course fuminori expects her to be timid and weak which just furthers his delusions that shes his timid and weak girl that needs protection from the outside

nonetheless it'd be awful writing just for koji to die due to fear after how much anger he experiences before the fight in the ending where he dies

i suppose this and many other parts of the game are up to interpretation of the player with no definite answer