Quick instructions to let you hop in right away
A deeper dive into the character and the playthrough
Reimu is the older of the two main protagonists in the Touhou Project series, being present in every single (main series) game from the first one onwards. She's a somewhat put-upon shrine maiden who is responsible for the management of the Hakurei Shrine and resolving incidents in the primary Touhou setting: Gensokyo. This tends to involve large amounts of shooting things until they go away, which should translate just fine into Terraria, right?
Reimu plays pretty normally for the most part. Other than a few interesting quirks, it's mostly about making the most of the weapons you're given.
Reimu starts the game with the Dao of Pow.
An unwieldy, difficult to control contact damage weapon that's literally a Yin-Yang Orb? No way I could resist the Touhou 1 reference there. It's the first weapon Reimu ever used in the series, so of course she starts with it. It's fantastically overpowered for this stage in the game, but you'll be stuck with it for a while and flails can be unwieldy for taking down bosses. Admittedly...I'd written this spec before 1.4 gave flails in general and the Dao of Pow in specific a huge buff, and I couldn't really bear to change it. That's okay though, Reimu is OP protagonist tier anyway.
Reimu starts the game with a Tortoise Saddle.
The Touhou Project games (barring Touhou 1) are vertical shoot-em-up style games, so naturally the protagonist needs to be able to fly. Originally, though, Reimu wasn't able to do so unaided. Enter Genji: A flying turtle who Reimu rode around while trying to figure out who'd made a mess of things THIS time, until she eventually figured out how to do it herself. Since Touhou 6 was a significant series reboot, many players have only played later games, and Genji hasn't appeared since Mystic Square (the fifth game in the series), it's likely that a lot of people don't know about him.
Of course, there are no flying turtles in Terraria (much as there are no buses in Gensokyo), so she'll just have to settle for a land-bound tortoise. Same thing, really. Don't @ me, marine biologists.
Reimu may research and duplicate banners
Not much to say about this one, other than that I'm glad there was such a good translation for the ability to create and place talismans that ward off youkai in the game. With this, Reimu can perform her duties as a shrine maiden properly and help guard against the variety of monsters present in Terraria, too...at least, once she's killed enough of them. There's less need to farm enemies in a character playthrough, but it can help with troublesome enemy spawns during boss fights, the Lunar Events, fighting off repeat invasions, and any farming for non-weapons you might want to do.
Reimu receives the Tome of Infinite Wisdom upon defeating Skeletron, but may not use the right click attack.
Reimu has been able to use ofuda (Japanese paper talismans) as a method of attack since day one (well, game one), but the closest we have here in Terraria is a book on a stick that fires paper at enemies. I guess they could look like talismans if you squint and assume there's stuff written on the side of the paper that you never get to see. Sadly, they don't home in on enemies like many of Reimu's attacks do. It should help against the Wall of Flesh (decently ranged attacks being practically mandatory there), plus it makes the dungeon easier and should remain a little relevant even after receiving the Rainbow Rod.
Arguably Reimu's most iconic bomb, Fantasy Seal has seen a lot of use over the years bursting down troublesome bosses and getting Reimu players out of a tight spot, as is the ultimate purpose of any bomb in an STG. At its core, though, it's just a bunch of multicolored homing projectiles, and Terraria fortunately has its share of those. It's not as though we can replicate the screen-clearing feature here...well, until we get to Marisa, anyway. The Rainbow Rod's homing and piercing capabilities make it a good choice against the mechanical bosses, with the explosion effect making it particularly devastating against The Destroyer. Once the three mechanical bosses have been taken down, Nightglow offers a frankly overpowered option for the fight with Plantera that potentially remains useful through to endgame.
Reimu receives her choice of a Stake Launcher, Stynger, or a Nail Gun upon defeating Plantera. Reimu may use the two weapons not chosen, if acquired.
The other mode of attack Reimu is most known for as a playable character, Persuasion Needle fires a barrage of needle-like projectiles straight forwards to shoot down enemies. Here in Terraria we're actually somewhat spoiled for choice on how to represent this, so I decided to give the player their pick. Choose the Stake Launcher for the most true-to-character interpretation (they don't pierce in Touhou, unless I missed a game where they do, but they certainly don't explode either), or just pick whatever takes your fancy.
Personally I feel like the Stynger bolts look the most like actual needles, but the cluster bomb functionality isn't really a good match. Maybe pick the one you'll have the most trouble finding otherwise? You can always go do the Pumpkin Moon/Solar Eclipse/Golem farming to acquire the other two, if you want to get fully decked out. Whatever you decide, these options plus Nightglow are going to have to carry you through the rest of the game, so choose wisely.
Oh, and if you're wondering why she doesn't get free ammo, it's because she's supposed to be poor. Such is the life of an underappreciated shrine maiden.
Reimu may have God Mode enabled while Betsy is spawned
I'll admit, I just think this spell card sounds cool as hell and wanted an excuse to include it. ZUN does like his over-the-top spell card names at times, but that's part of what makes Touhou charming. It's also a good example of some of the more esoteric abilities character specs can include, and I wanted Reimu to be a good introductory character for concepts like this.
As for what it's used for...well, it'd make farming up the second tier of Tavernkeep armor easier, but she doesn't get any summons or sentries...hmm. Well, it doesn't HURT to have, at least. Some of that armor is pretty good even without the summoning benefits, after all.
And yes, you do have to turn god mode back off again after slaying the dragon.
[MOD NOTE: If you mod other dragons into the game, she gets this against them too]
After defeating the Moon Lord, Reimu is no longer subject to any challenge restrictions on items
This is just for fun, obviously. There's a few jokes in the fandom about "Reimu hax" or Reimu just being plain OP, and having her freed up to do whatever the hell she wants seemed like a fun thing to slap in here as a result. Although, why would you keep playing after defeating the Moon Lord, anyway? I guess beating him up with the Dao might be good for a laugh. Or better yet, a Wand of Sparking.
Reimu may turn on God Mode after defeating the Moon Lord
This is even worse! Although, it's not like I could give her this ability at any point before you're basically done with the playthrough. It's the name of Reimu's Last Word spell in Imperishable Night, and ZUN describes it thus:
A secret technique which is extreme in many ways. With Reimu's ability to float, she floats away from all sorts of things and cannot be attacked. If it wasn't just for play (with time limit), no one could beat her using any method
Guess she's decided to stop playing around. Terraria isn't governed by the spell card rules, after all.
Trivia fact: The Japanese name for this technique romanizes to "Musou Tensei", and it's a reference to the special attack of the same name from Fist of the North Star (albeit with different kanji and thus a different meaning). This is far from the only time ZUN adds references to weird things into Touhou games or other media. I guess he's kind of a nerd, huh?
Notes about items and features from mods that may enhance the experience if used.
Under construction, but check out Gensokyo mod; I'll add details on how that works with Reimu in the future.