Just like its sister series, Seihou has some nasty bosses up its sleeve.
- Marie is a very nasty Wake-Up Call Boss, especially on harder difficulties. Throughout most of her fight, she sends out lots of bullets that bounce off the walls quickly in both directions, usually right before a quick laser attack. In addition she also spawns little spaceships during her laser attacks, which can trap you if you don't kill them quickly enough. She requires good luck and reflexes, and may God help you if you're doing a no-bomb run.
- Both extra bosses are infamous for being very difficult.
- Marisa's fight is often a hectic Luck-Based Mission. While many of her attacks are decently dodgeable, being caught in the corner, or having Marisa spawn too close to you can quickly take off a life. Special mention goes to her most difficult attack (pictured above), which comes out very fast and will trap you if you're unlucky, and her final phase, which will become a mess of fast purple bubbles if you don't kill the correct clone quickly enough.
- Reimu is one of the most infamous extra bosses in either Touhou or Seihou. All of her attacks are either quick, dense, or both, she moves around the stage a lot, and she generally requires a lot of practice and memorization to be beatable. Her second phase is the most infamous by far, and the biggest obstacle in clearing the stage. While it does have a strategy note , it's easy to fall to the bouncing yin-yangs, and the fast and random yellow bullets.
- Marie can become one when doing scoreruns, mostly because of her EX attacks. In scoreruns, you generally try to play defensively, and graze as much bullets as possible. Marie's EX attacks are quick homing lasers that are hard to see, and will interrupt evade chains. Even worse, the missiles themselves cannot be grazed, so good luck dodging them while trying to keep your evade combo active.
- Muse is this if you don't know what you're doing. Her defense is ridiculously high, and only a few attacks work against hernote . By not using the right attacks, she will stay alive for a long time, and constantly spam her charge attacks, which get more dense every time they're used.
- Yuuta Kirishima in the C67 version is another Wake-Up Call Boss. Many of his attacks require quick reflexes or come in from strange angles. His final attack on Hard and Lunatic takes the cake, as it eventually becomes so fast, it's almost impossible to react to the lasers that come in. Thankfully, he's much easier in the C74 version.
- Hirano in the C67 version is much more difficult than VIVIT-r, who can be dealt with once memorized. Hirano loves to spam fast and dense homing bullets while many dense bullets are already on screen. She requires quick reflexes and the ability to dodge dense bullets.
- Lagunas in both versions is also a pain.
- In the C67 version, you effectively have to memorize his whole fight in advance. He uses very fast bullets with tricky patterns, misdirecting them incorrectly will lead to death, and his last attack seems almost undodgeable. It's made even worse if you're using a slow character. Hope you brought enough bombs!
- In the C74 version, he starts out rather easy, but things get worse once Yuuta joins his battle, when both of them start shooting fast bullets in all directions. Their penultimate phase has a lot of health, shoots awkwardly moving bullets from the side, and you can't even shoot him half the time. Even worse, bombs no longer provide invincibility, so unless you're using Hirano A's screenclearing bombs, you're in for a tough fight.
- All of the extra bosses are difficult to some degree, but Muse is the hardest by far. Muse has a a lot of HP, loves teleporting around the screen, and using dense homing attacks (even referincing her level 2 from KG). Her worst attacks are her second and final. For her second, you're trapped in a small circular area, where you can't shoot the walls, and can only hit Muse with the (often weaker) homing focused shots. For her last, the "laser walls" pulse and curve around the screen (you can't shoot them, either), and she shoots a fast homing cross if you kill one of her puppets