Wow, the weekly reading load for these portions is a lot, haha. I’m so behind… 
際(に)
際(に) is used to indicate a special occasion on which someone does something, so the phrase can’t be used on common occasions.
Only Vinf or N or demonstrative adjectives この, その, あの can be used before 際に. Vinf・nonpast and Vinf・past indicate incompletion and completion, respectively, in relation to the action in the main clause.
The particle に of 際に may be dropped. When に is dropped, the focus shifts from the occasion to what is described in the main clause.
際に is a formal expression that is often used with Sino-Japanese words. In the examples given in note 4 in which neither a Sino-Japanese verb/noun nor a honorific polite verb is used, 際に is unacceptable.
N に際して is more formal than N の際に. When the former is used, N has to express a very special occasion. If N expresses an occasion which is not so special, N の際に can’t be replaced by N に際して.
際に indicates the time when something special takes place, whereas 折に indicates an occasion when something ordinary takes place.
There is another expression 場合, “case”, which is used in the form of Vinf 場合 or N の場合. 場合 means “a suppositional case”, so an event that precedes it may not take place. So if the event is a real event, 場合 can’t be used.
Here are a couple 際に examples from the Tokyo Joshi Pro Wrestling press conference on 2024.01.09 wherein Juria Nagano announced that she would be retiring from wrestling:
Here’s the video, and here’s the official transcript.
長野「今回は私のことでこのような場を設けていただき誠にありがとうございます。私、長野じゅりあは4月13日をもって東京女子プロレスを卒業することとなりました。理由と致しましては今後は芸能の仕事によりいっそう力を入れていきたいというところがありまして、その際にプロレスが中途半端になってしまうのが自分としても嫌だなというところがありまして、このような決断をいたしました。また昨年、手の骨折もあり、その際に半年間ほど仕事ができなかったという状況もあり、今後の人生プランを考えた時に卒業しようと自分の中で決めました。プロレスラーとして叶えたかった夢とかやりたかったことはまだまだたくさんあります。ですが、長野じゅりあとしてやりたいことややらなきゃいけないこともあり、今回このような決断に至りました。プロレスを始めてから2年間、本当に逃げ出したくなる時とか、辛いこととかもあったんですけど、それよりもリングに立つのが楽しくて。応援してくださった皆さんの声援がすごく力になりました。感謝しています。プロレスを続けてきて東京女子プロレスの皆さんがすごくやさしくて。先輩方とかも私、人見知りなんですけど最初からいっぱい話しかけてくれたりとか、練習を遅くまで見てくださったりとか、後輩も入ってきて、すごくいい環境でできたなと思っています。本当にこの環境でプロレスができたことに感謝しています。卒業まで3ヵ月あるので、プロレスラー・長野じゅりあとして、燃え尽きるまでしっかりと闘っていきたいと思います」
Nagano: “Thank you very much for giving me this opportunity to speak. I, Juria Nagano, will be graduating from TJPW on April 13. The reason is that going forward, I’d like to focus more on my work in the entertainment industry, and I don’t want to thereby end up pursuing pro wrestling half-heartedly, so I came to this decision. Also, I broke my hand last year, and I was unable to work for about six months, so when I thought about my plans for my future career, I decided to graduate. I still have dreams and things that I wanted to do as a professional wrestler. However, there are also things that I want and need to do as Juria Nagano, so I came to this decision. Since I started wrestling, for the past two years, there have been times when I really wanted to get away from it, and there were times when it was hard, but above all of that, I enjoyed standing in the ring. The cheers I’ve received from everyone supporting me have given me incredible strength. I’m grateful to all of you. Everyone at TJPW has been incredibly kind to me as I’ve kept going with pro wrestling. I’m a shy person, but from the very beginning, my senpais have talked to me a lot, and they’ve watched over me during practice until it got late, and new juniors have also joined, and I think everyone has made it a really nice environment. I’m truly grateful that I was able to do pro wrestling in this environment. I have three months until I graduate, so I’m going to fight hard as the pro wrestler Juria Nagano until my flame burns out.”
さすが
さすが expresses one’s strong feeling that something has turned out as one expected, or that something has turned out to be contrary to one’s expectation, and as one has not expected (Japanese sure doesn’t like to make things too easy for us, huh?).
In the structure さすが は X だ, は can be omitted.
さすが~だけ may take either あって or に.
In the case of さすが の X も, the speaker wants to say that something has occurred contrary to what one can expect from the characteristics of X.
さすが can be used like an exclamation in conversational Japanese.
The related expression note tells us that やはり / やっぱり is similar to さすが. However, やはり does not express the strong feeling of fulfillment of expectation that is expressed by さすが. やはり does not have prenominal nor pre-copula use.
I don't see さすが nearly as often as I see やっぱり in TJPW, but I found one from the 2024.02.10 show after Yuki Kamifuku challenged Yuki Arai for the International Princess title after Arai successfully defended her belt against Juria Nagano:
(No video because this happened in the ring.)
荒井「初めての防衛戦ということで、卒業が決まっているじゅりあちゃんがベルトに挑戦することはきっとすごい勇気のいることだったと思うので…すごい強い気持ちを感じる試合で、自分も闘えてよかったなと思いました。ありがとうございました。私はこの後も誰が相手でもベルトを守って、もっともっといろんな景色を見ていきたいなと思いますので、これからも応援よろしくお願いします(ここで上福が登場)」
Arai: “This was my first title defense, and I know it took a lot of courage for Juria-chan, who will be graduating, to challenge for the belt… I really felt her strong feelings in the match, and I’m glad that I was able to fight her, too. Thank you very much. I want to keep defending my belt from here no matter who my opponent is, and I want to see even more different scenery, so please keep supporting me.” (Kamifuku enters)
上福「お疲れ様~。試合直後とは思えないくらいのこの美しいビジュアル、さすがだなって思うし。本当にいつも東京女子プロレスとアイドル業と、どっちもすごい頑張って。名古屋と東京どっちも行き来して忙しそうにしてるのに『忙しいでしょ? 疲れてるでしょ?』って聞くと「いや~、そんなことないです」って言えるかんじ。もう全然鼻についてないよ。愛されてるところとかも全然ひがんでないんだけど、まぁ私も東京女子プロレスを盛り上げたい気持ちはあるのね。最近は色んなアジアの国に行って、よく分からない食べ物食べたりして頑張ってるんだけど、ここで東京女子プロレスを盛り上げたい。そしてビジュアルを大切にしている同士、お互いの顔面を崩し合って、そしてこのベルトを懸けて闘いあったらもっと盛り上がるんじゃないかなって思うんですけど~」
Kamifuku: “Great job! An unimaginably beautiful visual right after the match, as expected. You’re always working so hard both in TJPW and in the idol industry. It’s like how even though you seem so busy going back and forth between Nagoya and Tokyo, when people ask, ‘You must be busy, huh? Aren’t you tired?’ you’re like, ‘No, not really!’ I’m not at all sick and tired of it. I’m not at all jealous of how much they love you!! But, well, I also want to liven up TJPW. Lately I’ve been going to different countries in Asia and eating foods that I don’t really understand and working hard, but I’d like to make TJPW more exciting right here. And I thought, wouldn’t it get more exciting if we two people who care about looks break each other’s faces, and fight with that belt on the line?”
せい
せい is a dependent noun, so it needs a modifying word, phrase, or clause. せいで is used only when the result is undesirable (example (1) b. gets the full three Michelin question marks, haha). せいか, however, is used whether the result is desirable or undesirable.
Example (2) c. has 気のせい, which I personally think of as a specific word in and of itself rather than 気 + the せい structure…
せいで is used when the speaker finds the cause of an undesirable result to be beyond their control. So if the cause is within the speaker’s control, せいで can’t be used. But せいか has no such restriction.
せい can’t be used to express a reason.
おかげ and せい are similar in that both express a cause, but the difference is that おかげ is used when the result is desirable, and it also implies that the person who attained the result is thankful for the cause. おかげ is sometimes used with an undesirable result for the purpose of sarcasm.
ため(に) can also express a cause (as well as a reason). And unlike せい, ため(に) doesn’t have the same restrictions.
I see せい fairly often in TJPW, usually used by the wrestlers when pointing blame at whoever took the pin in their team (thus costing them the match), haha. Here are several examples from the 2024.01.13 show after the team of Miu Watanabe, Pom Harajuku, and Rika Tatsumi lost in the main event (due to Pom getting pinned):
Hard mode: here’s the video. Further context is that there was a bit of friendly fire in this match, which certainly was not an おかげ situation for Pom…
未詩「神戸で私は山下さんと前哨戦でもあったんですけど。あらためて挑戦者に決まってからすごい強みを感じたんですけど、でもあと3カ月近くあるので頑張りたいなと思いました」
Miu: “In Kobe, I had a preview match with Yamashita-san. I felt her amazing strength anew after being chosen as her challenger, but we have almost three months to go, so I wanted to try to do my best.”
辰巳「それもあるし、タッグのトーナメントも始まるので。せっかく白昼夢もいるし、ぽむもいたので勢いつけたかったなっていうのと、あとみずぴょんのご家族の方も来てたので。私はすごいアピールしたかったので…でもやられてしまって、ちょっと複雑な心境ではあります。でも明日もあるので気合入れていこうと思います、岡山」
Tatsumi: “There’s that, and there’s also the tag tournament starting. We were together as Daydream, and Pom was also there, so I wanted to gain some momentum, and Mizupyon’s family was there, too. I wanted to really show off for them… But I lost, so my feelings are a bit mixed. But we have tomorrow, too, so I’m going to give it my all at Okayama.”
ぽむ「なんだか今日は相手のチームがすごく強くて。白昼夢と組んで今日は心強ーいって思ったはずなんですけど、終わってみて、あれ? なんかすごい味方からもやられた気がするんですけど」
Pom: “The other team was really strong today. I was teaming with Daydream, so I felt veeeery reassured, but looking at it after the fact, I feel somehow like I also got really beat up by my teammates!”
辰巳「ぽむのせいだよ」
Tatsumi: “It’s Pom’s fault.”
ぽむ「ぽむのせいじゃないですよね?」
辰巳「完璧にぽむのせいです」
Tatsumi: “It’s completely Pom’s fault.”
ぽむ「はい、すみませんでした!」