No.
The way he's crafted as a character, and the upbringing he's experienced means that he's milder, mindful, non confrontational, and low-key timid.
The reason he follows him is because is Ido's Brother + someone in a higher social status than him, and he has no reason to think that he's a rapist. Just a man that doesn't like him.
He does signal his bodyguard, and notices that the bodyguard does follow him, that why he doesn't feel too conflicted in going into the bathroom is it.
When Ido's brother does start to act, Sejin thinks
"We're both men, I can push him and run away...so then why am I so afraid?"
He's clearly aware of the fact that he is, probably capable of protecting him. The dialogue establishes that he probably can it's is a MENTAL BARRIER that is stopping him from doing so. Sejin has the tiniest bits of memories from his past life, and If you see the chapter they start to seep in during that scene- he's traumatised, he starts to get flashbacks from his previous life. Trauma makes people behave in ways that seems odd from the outside. But he GENUINELY feels that there's no way out.
Not to mention their secondary characteristics at and Alpha and an Omega brings another level of fear.
Additionally, someone being 'scared' or a 'dAmSel iN dIsTrEsS' does not mean that they're incapable of being smart. What Sejin has is 'book smarts' or 'Academic Intelligence' not 'How to sudden forget all your trauma, and magically keep a rapist at bay'.
Also, you saying that 'You could just kick them in the family jewels....I know It's effective...I've done it' is IRRELEVANT. You have that knowledge, Sejin is a wealthy person who probably would have been in a situation where he would have to protect himself and not his bodyguard. He won't just be able to pull some fighting knowledge out of his ass.
Yes, Sejin does have a decent build and a healthy body, that man has a BIGGER BUILD, and a STRONGER BODY. An ALPHA.
Sejins character is that of someone who is soft, mild, non confrontational- someone who has always compromised, and someone who is traumatised. Not every person, man, has to be able to strike someone precision, and no second guessing- they don't have to be all Macho and strong.
He is a realistic character.
Fear can make people stop in the face of things they can certainly do- trauma aswell
I don't like Ido. It's so obvious that he was the guy from Sejin's dreams. It's probably both him and his brother who grape Sejin. He's so shady.
I also kinda feel conflicted about Sejin following the grapist to the bathroom and then on the next chapter he was portrayed as someone smart.
The MC is definitely not written to be someone smart. He's the whole definition of a damsel in distress.
Who the f would follow someone who talks shit about omegas into some place private with reasoning "I have no other choice." Tanga!
It's the number one rule of survival to keep yourself in a crowded places when someone's obviously trying to harass you, don't go anywhere with them alone.
No matter if he makes a scene, if there's people around, you're bound to get help or witnesses at the very least. You even have a frickin bodyguard you can go on to to ask for help on keeping you safe, but instead, you'd rather walked past your bodyguard silently without even so much as giving him an order to call anyone for help and follow your assailant's ass past two public bathrooms when you could've stopped and insist on going to the first bathroom you see.
"I can protect myself" my ass.
You didn't even try. You just rather kneel down and cry like a powerless woman you're not.
You could fuckin kick them on their family jewels and when they bend down from pain give them a knee on the nose bridge to knock them out. I know it's effective, I've done it myself too many times in highschool. I know no other women who would gone down without a fight Infront of their perpetrators what more a fuckin man who obviously has a considerably good build and healthy body.
I like Sejin, but also hate how they would try so hard to paint him as someone smart when nothing about him is smart. Just say he's a damsel in distress, don't make up lies you couldn't support.