It’s probably ておく grammar point:
https://japanesetest4you.com/flashcard/learn-japanese-grammar-42/
which indeed mean: to do something in advance/to prepare for something in advance. The context helps as well:
記憶は薄れるから = because memory will fade
記録しておくんだよ = I’m recording this in preparation of that
Wow, I’m positive that I’ve heard もったいない a ton in anime but I’ve never looked it up before
Great! I hadn’t come across that grammar before. Knew I must have been missing something.
I have a board game called もったいない 
Finally finished this chapter…This was harder than Chapter 1 (for me)! but I did it yatta! so take that mean 'ol crabigator!
Sometimes I feel like I took on way too much…then I see the panel on the last page and it made me laugh. I can’t wait until my skills are at your folks level and reading is easier! Also hope the next chapter isn’t any more difficult…and the next book has so much text it’s scary! 
By the end of this though…I hope that with the knowledge gained from this first manga I’ll have actually been able to read and cover to cover …along with all the grammar I’ve learned (from this book) and am still learning (bunpro - almost done with N5) …I’ll be ready to conquer our next book!
Well I haven’t read this chapter yet, but here’s chapter 5.
As long as the threads keep coming! 
Oh man this chapter was difficult! Just finally finished it. I hope the next one is a bit easier!
so far it is
Maybe because 湯 and 温 look a lot alike, have vaguely related meanings (heat), and are learned close together? 
I know my brain keeps switching them.
湯 actually means specifically hot water, but I can see how a word like 温泉 could muddy things a bit
I know, that’s why I said vaguely. But the idea was that hot water still brings to mind heat and looks similar enough to 温 that it’s easy enough to confuse.
Phew, chapter four was tough!
But, thanks to the vocab list and this amazing thread, I’ve made it to the end!
Well, bar soon and future re-reads, and watching the anime with book in hand too!
Thank you again to everyone involved in putting together the vocab list and this discussion, it is amazingly useful to me now and will be to many people in the years to come I am sure. Thank you so much!
Jokes aside, it’s nice to see your progress through the book this way, @marcusp! Thanks for taking us along!
This is both beautiful and horrible
気持ち悪い気持ち悪い気持ち悪い
罪罪罪罪罪罪罪罪罪罪罪罪罪罪罪
I recommend sticky notes.
it’s nice to see a lot of my “stupid” questions are helping others 
I reject that reality. In my mind canon, you are simply writing on a photocopy of the book. Yep, that’s definitely what it is.
I thought @Belerith tagged me because of the whole “thread being useful later” thing. But I didn’t notice the picture until your comment so now I’m wondering if it was because of that.
Apparently on Amazon and eBay, selling a used book that’s been written in can still be considered “good” condition. Maybe not to the extent of what @marcusp did, but I still find it strange how it can be considered anything but “poor” condition.
Yeah, it was because of the picture. Thought you might despair enjoy that. 
