たとたん (ta totan)
Meaning: as soon as; just as; the moment; the instant; just (now, at the moment)
How to use the: Verb (casual, past) + とたん
Describe the situation after the action, the change that happened before that immediately after that the action or other change happened again Because of the surprise and unexpected feeling, unexpected after the sentence does not show the action or the will, the command of the speaker
Yūmei ni natta totan ni, kare wa ōheina taido o toru yō ni natta.
He showed an arrogant attitude right after being famous
Shiken shūryō no beru ga natta totan ni kyōshitsu ga sawagashiku natta.
As soon as the alarm bell rang to end the exam time, the classroom was noisy
Natsu ni haitta totan, atsuku natta.
As soon as summer began, it became hot.
mado o aketa totan, tsuyoi kaze ga haittekita
As soon as I opened the window, a strong wind came in.
In the latter case, describing the speaker’s willful act (intention, purpose), then don’t use this sentence, right have to use sentence 「とすぐに／やいなや」
Watashi wa ienikaeru to sugu ni o furo ni haitta.
When I got home, I took a shower immediately