Talk to the Impatient Biologist after defeating Nergigante and he should give you this quest, although you may need to have complete the optional quest Talons of Ire and Ice, first. Once it’s unlocked, be sure to prepare ahead of time. Everything that held true for low rank Kirin goes double for high rank Kirin, and the attacks are all the same, it’ll just take more damage to put down and punish you more severely for mistakes. Fortunately, you have more skill options at your disposal now.

Thunder resistance is still a must, obviously, and you should endeavor to attempt to reach a Thunder resistance score of twenty at a minimum. Not only will this reduce the damage you take from most of Kirin’s attacks, but it’ll also outright prevent Thunderblight, making you less likely to get stunned, and considering that two bad strikes from Kirin can be fatal, it’s a great security against getting carted. Even if you have to sacrifice some offense to hit this threshold, it’s probably worth doing.

You can - and should - come equipped with the Thunderproof Mantle, but you may not necessarily want to rely on it to get your Thunder resistance up to snuff. It has a finite duration, after all, with a significant down-time, but it’s still handy for reducing Kirin’s damage while in effect. You should also endeavor to eat a meal that gives Elemental Resistance Up (L), if possible, and if it fails to also max out your health and/or stamina bars, consume objects in the mission to make up the difference (Mega Nutrients, Max Potion, Well-Done Steak, etc). The +15 bonus to all your resistances is worth getting.

The skills and resistance granted by your weapons matter a great deal, but don’t leave out weapon considerations, either. While elements have been more or less a somewhat useful curiosity up until now, after defeating Nergigante you should have gained access to materials that seriously raises the possibility of reaching the end of various weapon trees. At this point, weapon selection can matter significantly more than it did before, and is worth putting some thought into. There’s no getting around it - for foes this fearsome, you’ll need different loadouts, and enemies aren’t going to get any easier going forward, so crafting and upgrading the gear you need now and in the following quests and changing your loadout - even if it means abandoning a favored weapon for one that performs better against a specific monster - may make your life easier. In Kirin’s case, it’s weak to Fire, so focus on that if at all possible, or failing that, consider a weapon with the Blast Ailment, as Kirin isn’t terribly strong to it, and the extra damage is always welcome.

Another option to consider with Kirin and all future Elder Dragons is to make use of Elderseal weapons. Most monsters will - upon violent provocation - grow enraged, and that goes for Elder Dragons, too, although their rages tend to be more… signature, than the tantrums of lesser monsters. Kirin, for example, charges up, and grows much more dangerous with its lightning attacks and takes less damage save for head shots. You can, with the use of Elderseal weapons, retard the power of these abilities, albeit temporarily. In the case of Kirin, striking the monster while it’s charged up will reduce the defense boost it gains while charged up, making other parts of its body vulnerable to damage again. It’s… honestly not much, and if you can hit the head somewhat reliably, you should just stick with fire damage, but it’s something.

Unfortunately, the rewards for completing this task aren’t in any way a match for the trouble of killing High Rank Kirin, but the practice will serve you well for the future, and the materials should unlock the High Rank Kirin armor sets.