Thank you for all your help. Excuse my anonymous request.
The genre is tickle, please. The main character is a girl with long silver hair who has difficulty expressing her emotions. She uses polite words (not honorifics) such as "I won't miss it" and "Stop it! ......!" She speaks in polite language (not honorific), such as "I won't miss it," "Stop it! The attire can be anything as long as there is (important) innerwear or a suit that covers the upper half of the body including the arms tightly.
He is ignorant when it comes to tickling, but he is tolerant and can remain calm under a certain amount of blame. However, his armpits and surrounding areas are particularly vulnerable, and he is distraught when he is tickled on his bare skin.
The situation does not specify the historical background, but the blamer may be a hardened or hardened woman. The blame should be placed on a group of flesh tentacles that can harden and emit slippery mucus. The girl who has come to defeat the tentacles is supposed to have cornered them, but is instead led to the nest of the swarm and caught.
We would like at least half of the story to take place before the girl is restrained by the tentacles. When the girl is restrained, her elbows and knees are swallowed by the sphere of the tentacles and she is in the human figure. The upper half of the body is being forcibly extended by being pushed from behind, please.
At first, please feel as if you are calmly asking for an opportunity, with mitigation by the thickness of the innerwear and the tolerance of the person in question. I would like you to relentlessly torment him between his arms and armpits with the tentacles that have invaded through the cuffs of the innerwear. I want you to tickle me directly in the armpit and make me laugh for the first time. Please make the time between the penetration and the start of the armpit tickling longer. Please use mucus as a tome blow. I want them to be distraught, and to laugh and writhe with no time to speak in a polite manner.