I’m a little iffy translating the 2nd bubble. From context, I know he inserted it into her and immediately stopped moving. However, I usually see 固まる in the context of hardening. Maybe it’s like how liquid stops moving when it hardens into a solid, so it also has the meaning of freezing in place? I really don’t have enough Japanese knowledge to say.

I want to translate it as “What’s wrong? As soon as you inserted it, you froze”, but I don’t want to post it until I get some kind of clarification about how 固まる is being used.

AlephFish said:

I’m a little iffy translating the 2nd bubble. From context, I know he inserted it into her and immediately stopped moving. However, I usually see 固まる in the context of hardening. Maybe it’s like how liquid stops moving when it hardens into a solid, so it also has the meaning of freezing in place? I really don’t have enough Japanese knowledge to say.

I want to translate it as “What’s wrong? As soon as you inserted it, you froze”, but I don’t want to post it until I get some kind of clarification about how 固まる is being used.

It's pretty much as you thought. If you wanted to be cheeky about it, you could even word it like "you stiffened up as soon as you put it in" and there'd be a little double meaning there. That kanji 固 is used in many words to impart the meaning of "being fixed," like 固定 which is used when something is "fixed in place."

NinjaPope said:

It's pretty much as you thought. If you wanted to be cheeky about it, you could even word it like "you stiffened up as soon as you put it in" and there'd be a little double meaning there. That kanji 固 is used in many words to impart the meaning of "being fixed," like 固定 which is used when something is "fixed in place."

That helped a lot, especially mentioning 固定. Thank you!