Translation reserved for Mangatopia.
If you translate this into another language, I request that you credit me as the original Japanese to English translator in your release. If you can't/won't do that, then don't use my translation.
Chapter 30: Incredulity Time
(right, sign) School entrance ceremony
(on Itona's badge) 1st year
(left, star) A li'l killer's knapsack!!
(far left, star) Assassinations are the talk of the town!! Publication of the "Majin Tantei Nougami Neuro" paperback and remix editions is going wonderfully!!
(bottom) Field trips and a transfer student!! With a large helping of both, volume 3 goes on sale 3/4 (Mon)!!
(Students): This guy
(sfx) Nom nom
(Students): and this octopus
(Students): are brothers?!
Are you serious...!?
Itona: As we are siblings, there is no need for petty tricks.
Itona: I will kill you and validate my strength.
Itona: The time will be after school.
Itona: We'll have a match in this classroom.
Itona: Today will be your final class.
Itona: Say your farewells to them now.
Yada: Wait a second sensei, what does he mean he's your brother?!
Korosen: No, no, definitely not!!
Mimura: To start with, humans and octopodes are completely different!!
Korosen: Geez, I don't know a thing about any of this!
Korosen: I was born and raised an only child!!
Korosen: If I'd pestered my parents about "wanting a younger brother"...
Korosen: then things would have gotten awkward!!
(right of mamaocto) So I've been thinking about our lifestyle...
(right of papaocto) Hrmm...
(Students): Do you actually have parents in the first place?!
(sign) Faculty Office
Box: Are they truly siblings?
(right of Shiro) Hahaha
Box: is this a strategy to unnerve him?
Shiro: I apologize for surprising you, Karasuma-sensei.
Shiro: That boy is a highly-classified secret, after all.
Shiro: It's fully understandable for you, who are on-site, to be uninformed.
Shiro: That being said, allow me to assure you.
Shiro: That boy is certainly Korosensei's younger brother.
Shiro: That much...
Shiro: will become evident to everyone after school.
Maehara: He's really packing those snacks in there.
Maehara: He's got the same love of sweets as Korosensei.
Isogai: Their expressions are both difficult to read, too.
Korosen: You're certainly comparing the two of us excessively, even when our status as siblings is under suspicion.
Korosen: It's quite irritating.
Korosen: To improve my mood, I'll just take a look at the gravure book I bought today.
Korosen: This right here suits an adult's tastes.
(Students): They're even the same in liking big boobs!!
Okajima: ...I can
Okajima: suddenly see them in a more realistic light.
Nagisa: Is that so, Okajima-kun.
Okajima: You bet!!
Okajima: We're all brothers when it comes to liking big boobs!!
(Nagisa): You three are brothers?!
Kayano: If they really are brothers, then...
Kayano: why doesn't Korosensei know about it?
Fuwa: I bet it's like this.
Courtier: Your majesty!!
Courtier: It won't be long before the enemy's forces reach us!!
King: Nuuu, there's no avoiding it!!
King: My sons!!
King: You alone must survive!
Korosen: You go on ahead, brother!!
Korosen: Once we cross this bridge, we'll be able to get away!!
Itona: Big brother!!
Itona: Big brotherrrr!!
Korosen: Don't worry about me, just go!!
Korosen: Live on,
Korosen: little brotherrrrrr!!
Fuwa: ...and then they grew up and began their fated battle
Fuwa: without realizing they were siblings.
Kayano: why is the younger brother the only human?
Fuwa: That's, well...
Fuwa: a mutation?
Kayano: You can't just explain away something that crucial!!
Hara: You're way too easy-going about getting to the bottom of characters' backstories, Fuwa-san!!
Hara: Work up more of a plot...
Box: If he says they're siblings...
Box: then there must be some connection to their history.
Box: He might know about the past Korosensei has kept hidden from us.
Box: The assassin transfer student Horibe Itona.
Box: I wonder just what he intends to show us.
(white sfx) School bell
Irina: A ring of desks...?!
Karasuma: Just like in a real match.
Karasuma: It's the first time I've seen someone set up an assassination this way.
Shiro: You must have had your fill of plain old assassinations, Korosensei.
Shiro: Let's settle on a single rule for this match.
Shiro: If you take even one step out of the ring, you'll be executed on the spot!!
Shiro: How about it?
Sugino: ...What the heck.
Sugino: Who would follow a rule like that?
Karma: if he violates a rule that has been decided in front of everyone...
Karma: then his credibility as a teacher
Karma: It would be surprisingly effective against Korosensei. His hands are tied.
Korosen: ...Very well, let's go with that.
Korosen: However, Itona-kun,
Korosen: causing harm to those watching will also mean defeat.
(Itona sfx) Nod
(Shiro sfx) Lift
Shiro: Well then, we'll begin on my signal.
(sfx) Badump badump badump
Box: Our eyes
Box: were all glued to the same spot.
Box: Sensei's lopped-off arm
Box: ...wasn't what had our attention!!
(sfx) Swoosh swoosh
Box: ...that explains it.
Box: His remaining dry in the rain despite being empty-handed
Box: was entirely due to those whirling tentacles.
(Nagisa sfx) Shudder
Korosen: Where did you get those!!
Korosen: Those tentacles!!
Shiro: We have no obligation to tell you, Korosensei.
Shiro: However, with this, you should understand.
Shiro: He has different parents
Shiro: and was raised differently,
Shiro: you and this boy are brothers.
Shiro: Still, that is quite a frightening face you're making.
Shiro: Has this...
Shiro: brought to mind something unpleasant?
Korosen: ...it would seem
Korosen: that I need to ask you some questions, as well.
Shiro: You won't be able to,
Shiro: seeing as you'll be dead.
Shiro: When exposed to this pressurized beam at point-blank range,
Shiro: your cells' viscosity will increase
Shiro: and your entire body will instantly go rigid.
Shiro: We know about every single one
Shiro: of your weaknesses.
(bottom right, star) Sliced and diced tentacles...!!