12-year-old trans girl Hannah is starting high school, though she's afraid of how other kids will react to her gender. At first, Hannah keeps it secret with the help of the school until she's ready. However, a student from primary school is there and knows, mocking Hannah for this. It becomes clear soon that her gender won't stay secret for long, and Hannah will have to deal with the fact while integrating into her new school.
First Day provides examples of:
- All of the Other Reindeer: Hannah is bullied by other kids for being transgender, while Isabella takes the lead.
- British Brevity: The first season has only four episodes running around 25 minutes each.
- The Bully: Isabella, a girl from Hannah's former school who knew her pre-transition and thus knows her previous name, bullies Hannah using this knowledge. However, over time she warms up to Hannah (who's very kind to her in spite of this, as she sees Isabella has suffered abuse due to bruises on her arms), and stops this.
- Coming-Out Story: Hannah comes out to Olivia first as a trans girl, who's accepting and keeps her secret. Later she also tells how she'd first done it to other kids (she's been forcibly outed in the present). She had told her mom and dad she's a girl from early on, but it took years for them to accept this. Afterward, one of the apparent girls she tells was inspired and he comes out to Hannah telling her he's a trans boy, but his mom never listens. After having heard this, Hannah vows to help him as best she can.
- Do Not Call Me "Paul": Hannah doesn't like being called by her former name (deadname) as is common for trans people. It's used by a girl who knew her pre-transition. She threatens to reveal it to everyone before Hannah eventually tells her this doesn't matter, she'll still be herself. When curious kids asked her before what it was, Hannah politely declined to say.
- Forced Out of the Closet: Hannah is outed as transgender on social media after starting with a new school. At first, it seems like her bully Isabella did it, but she insists it's untrue. It turns out she's right, and a boy from a higher up grade did this after learning Hannah's gender by overhearing teachers talking.
- Good Parents: Hannah's parents (and brother) completely support her in the present as a trans girl. The only rule which we see them lay down (not having a sleepover at kids' houses who don't know her gender) is for her safety.
- I Just Want to Be Normal: Hannah struggles with this, wanting to just be treated like any other girl but very anxious at first over how they'll react at her school if she's known as transgender. She makes loyal friends however who are accepting. The season one finale indicates that things have normalized for her.
- Malicious Misnaming: Hannah is bullied by Isabella, in part, using her deadname (which she knew due to them attending the same school before Hannah's transition).
- Market-Based Title: The Danish localization of the series is known as Hannahs hemmelighed ("Hannah's secret"). It doubles as an Artifact Title in the two last episodes given that she's outed at the end of the second episode.
- Nice Girl:
- Hannah is a very sweet, kind girl who just wants to have friends and live like her peers. She never bears any grudge toward her bully Isabella, and expresses concern about Isabella's bruises, knowing this means she's being abused by someone. Isabella is eventually even won over by her kindness too.
- Olivia and Natalie, Hannah's friends, also show her great compassion. Neither rejects Hannah after learning she's transgender, accepting it without hesitation, and Olivia even sets up a notification that shows all the positive comments about her online, as a way of offsetting the negative ones. When a girl gets her period suddenly at camp, Natalie also helps her at once, reassuring her that it's fine.
- No Periods, Period: Averted, a girl named Briony unexpectedly gets hers at camp and stains her pants. Luckily Natalie had put in a huge amount of sanitary supplies when she packed and gives her a tampon.
- Out of the Closet, Into the Fire: After Hannah is outed as a trans girl, she gets a lot of mockery on social media, more bullying, and soon loses one of her newfound friends, Jasmine. However, it's downplayed since most other kids are more curious than hostile, with the negative reaction blowing over quickly.
- Secret-Keeper: Hannah has Olivia promise to keep her secret as a trans girl after coming out, afraid of other people's reactions. She then gets outed to the whole school anyway, however (by someone else).
- Trans Tribulations: Hannah has to face being bullied, called her old name, a boy, and otherwise poorly treated over being transgender. Later a trans boy who was inspired by Hannah comes out to her, saying his mom flatly refuses to listen while he's trying to tell her about this.