To oblige somebody = to do somebody a favour. The woman is doing the couple a favour (at the request of the young woman) so she is obliging them.

‘When his arthritis kicks in, he has trouble walking’ Business at our cafe always improves when the warm weather kicks in. (takes effect) Kick in’ can also mean ‘contribute’ I’ll kick in $5 for the gift. There are also several slang and disrespectful ways to use ‘kicked’ to mean ‘die’. He kicked it. He kicked in. He kicked the bucket. ‘Oblige’ here means ‘help’. It’s pretty old-fashioned. You’d most often hear it as part of a set phrase. A:Thanks for helping. B: I’m happy to oblige.

This is a really interesting question. The first example sounds ok to me (but I would probably say “school starts/begins” instead), the other two don’t sound right. For me “kicks in” sounds like it implies an effect of something starting to happen/something beginning to take effect. E.g. “I’m feeling tired. I’ve just had a coffee. I’ll feel awake when the caffeine kicks in.” E.g. “she’s shy now but she’s just had 3 vodkas - she’ll be very loud once the alcohol kicks in”! E.g. “you might not think this song will be good at the beginning but wait until the beat kicks in, it’s great.” The second question is too difficult for me even as a native! I would never say this sentence, it’s very literary. To oblige can mean either to make someone feel like they have do something (e.g. I feel obliged to look after her because she is my sister) or to do someone a favour/say thanks (“I’m much obliged to you for your hospitality”) - kind of implies you feel you need to repay the favour. It depends on the context, I’m not sure which one from the text.

Hello Yara, I will try to answer your questions to the best of my ability. 1) I would not use that definition though it is sort of correct. The phrase "kick in" is not really something starting to happen. At least, the way it is used is more "start working (being effective". It is not literally working, but being effective. For example, many people use the phrase, "The medicine just kicked in," or "I'm waiting for the medicine to kick in" meaning to start working. 2) In this context, to oblige would mean to do a favor for. When someone obliges, it usually means that they are doing something for someone else, even if it is out of their way.

Kick in is more about something extra starting to join something that is aleady happening. For something that is starting independently you can use 'kick off', like in football. The concert kicks off at 9pm is ok. Personally I wouldn't use it outside of a sports context.