ところが

ところが introduces an outcome that is contrary to expectations.

USAGE:

• The first part sets up an expectation
• ところが introduces what actually happened (unexpected)
• Implies surprise or contrast with assumptions

DIFFERENCE FROM OTHER CONJUNCTIONS:

• ところが: emphasizes unexpected contrast
• しかし: general contrast, neutral
• でも/だけど: simple contrast, no surprise implied
• けれども: general adversative, can end sentences

COMMON PATTERNS:

• 〜と思(おも)った。ところが... (I thought ~. But then...)
• 〜はずだった。ところが... (It was supposed to be ~. However...)

Note: ところが always connects to the following clause; it cannot end a sentence.