敵てきのアジトへ突入とつにゅうするに際さいして、BGMとしてオールドスクールなラップを流ながした。
Upon storming the enemy hideout, we blasted old-school rap as our background music.

---

---

Read the explanation below to understand the nuance of how this grammar structure is used.

The Lowdown on the Nuance

～に際さいして is that formal-ass way of saying “when,” “on the occasion of,” or “at the time of.” But don’t go throwing this around when you’re just ordering a damn burrito. This ain’t your everyday “とき” (toki).

Think of ～に際さいして as the musical intro to a legendary hip-hop album or that heavy-ass moment right before a major heist. It’s used for big, monumental, non-repeatable life events—like signing a major record deal, dropping a classic LP, or starting a massive joint venture with another crew. It’s got a very proper, official, and public vibe to it. It looks back at the preparation or looks forward to the heavy responsibility that’s about to drop on your shoulders.

The Metaphor: Imagine Jay-Z stepping up to the podium to announce Roc Nation’s new global merger. He doesn’t say, “Yo, when we did this deal…” Nah, he says, “On the occasion of this historic partnership…” That’s exactly what ～に際さいして is. It’s the linguistic tailored suit you put on when big-time business is going down.

---

Check the blueprint below to see exactly how to stitch this grammar into your sentences without looking like a rookie.

Base Form	Grammar Point	Example	English Translation
Noun (Action-based)	＋ に際さいして	契約けいやくに際さいして	On the occasion of signing the contract
Verb (Dictionary Form)	＋ に際さいして	取引とりひきするに際さいして	At the time of making the deal

To lace this up correctly, you only have two options. You either drop a Noun that involves some kind of action (like 取引/deal, 引退/retirement, 設立/establishment) straight into ～に際して, or you use the Dictionary Form (Plain Form) of a action verb. Just remember, this shit is strictly for the future or the exact moment something major is kicking off. You don’t use it for some accidental, random-ass event like getting pulled over by the cops unexpectedly. It’s for the events you saw coming down the pipeline.

---

Read and master the example sentences below.

組織そしきの拡大かくだいに際さいして、新あたらしい武器ぶきを大量たいりょうに仕入しいれた。
On the occasion of expanding the syndicate, we sourced a massive stash of new straps.

金庫きんこを爆破ばくはするに際さいして、ダイナマイトの量りょうを間違まちがえてビルごと吹ふき飛とばした。
At the time of blowing up the safe, we messed up the amount of dynamite and blew up the whole damn building.

裏切うらぎり者ものを処分しょぶんするに際さいして、どの川かわに沈しずめるかで３時間じかんも議論ぎろんした。
On the occasion of disposing of the rat, we argued for three straight hours about which river to drop him in.

偽札にせさつを印刷いんさつするに際さいして、ボスの顔かおを透すかしに入いれてしまい全員ぜんいんに怒おこられた。
At the time of printing the counterfeit cash, I accidentally put the boss’s face in the watermark and everyone lost their shit.

対立たいりつ組織そしきと和解わかいするに際さいして、手土産てみやげとして最さい高級こうきゅうの葉巻はまきを持参じさんした。
On the occasion of making peace with the rival crew, we brought the highest-grade cigars as a peace offering.

法廷ほうていで証言しょうげんするに際さいして、映画えいがのセリフを引用いんようしたら裁判さいばん長ちょうに睨にらまれた。
At the time of testifying in court, I quoted a movie line and the judge gave me the ultimate death stare

密造みつぞう酒しゅを製造せいぞうするに際さいして、隠かくし味みに高級こうきゅうハチミツを入いれたら大だいヒットした。
At the time of manufacturing the moonshine, we added premium honey as a secret ingredient and that shit became an absolute hit.

闇やみカジノを開店かいてんするに際さいして、ディーラー全員ぜんいんにタキシードを着用ちゃくようさせた。
On the occasion of opening the underground casino, we made all the dealers rock tuxedos.

裏うら社会しゃかいから引退いんたいするに際さいして、記念きねんに金きんのピストルをプレゼントされた。
At the time of retiring from the underworld, I was gifted a gold-plated pistol as a memento.

密告みっこく者しゃを特定とくていするに際さいして、嘘うその情報じょうほうを流ながして罠わなを張はることにした。
Upon identifying the snitch, we decided to feed out fake info and set a trap.

---

Stay dangerous.