Dramas like
Twenty-Five Twenty-One

The recovery watch that is also a real match. Same 1990s setting, same coming-of-age register, and Choi Hyun-wook, who played Ji-woong, in a lead role. Time travel, a school band, and a boy meeting his own father at eighteen. Difference: it is a much warmer show, and the family at its centre is the point.

Hooks early Episode 2, once he lands in 1995 and meets his father at eighteen.

The same story told from the other end: two people who were everything to each other at nineteen, forced back into a room together at twenty-nine. Same documentary framing device, same precision about how memory lies. Difference: it lets them work it out. Where 2521 says the times were against us, this one says we were just young and bad at it.

Slow start Episode 3, once the documentary footage starts cutting between who they were and who they are.

If what you loved was the group rather than the couple. One alley, one decade, and five kids whose friendship the show takes more seriously than the romance. It is the reference point 2521 was consciously written against. Difference: it is engineered to be safe. Nothing in it will do to you what episodes 15 and 16 did.

Slow start Episode 3. The first two are scene-setting and the neighbourhood has not clicked yet.

Watch this one to heal. Athletes, a training-centre cast, and a first romance that is uncomplicatedly good for both people. Difference: much lighter and far smaller in ambition. This is the palate cleanser, not the successor.

Hooks early Episode 2, once the two leads start colliding on purpose.

For the specific ache of a love the times refuse to allow. Twenty-one episodes of war pulling the same two people apart, with yearning at 2521 intensity or higher and a female lead written with real spine. Difference: it is a war story before it is a romance, and it charges you far more on the way.

Hooks early Episode 2, once the war arrives and the tone hardens permanently.

The doomed-grandeur version instead of the recovery version. Every frame composed, every relationship on a historical clock, and a script that treats love as something history can simply overrule. Difference: unambiguously tragic and considerably slower. Go in knowing.

Slow start Episode 5, once all three men circling her are in play. The opening hours are a history lesson, and the real barrier is the writing register: the dialogue is elliptical and the flashbacks last seconds, and that is where it either has you or loses you.

The short one. Sixteen episodes, a Busan classroom, first-generation idol obsession, and a first love that is funny long before it is sad. Difference: it is a comedy first, and the guess-the-husband structure means you spend the show playing a game rather than dreading anything.

Hooks early Episode 1. It moves fast and the fangirl comedy lands immediately.