Ariel-Hime, I'm not clear about who's Rena (Ichika or Itsuki), but with the last chapter (74) we can parcially discard Ichika. Why she didn't tell to Fuutarou that she's Rena? if she only wants Fuutarou for her, Why she used such a dirty way to confess?. And Itsuki (in my opinion) is the last one to get a develop with Fuutarou (maybe in her arc, she admit to be Rina xd) ifk these ar just ideas. btw you're good with details.

...so in the end Itsuki was Rena (at least the recent one)

Now the question is, was she also the Rena from the past?

It is Itsuki, it was revealed last chapter

Yes, the adult one is clearly Itsuki!

I was thinking about the child one, at the moment it's not clear if she was Itsuki, another sister, or even multiple sisters!

Probably the little one is also Itsuki, but who knows?

There are little hints that could bring to other roads...

It seems that also little Rena was Itsuki, at least from some words in chapter 80.

Still think about a quintuplet game at the time.

well the backside of chapter 84 confirms that Ichika was the Rena of the past.

^ Could be, or Fuutarou met more than one Lolikano in the past, in which case the "Rena" Fuutarou referred to (the one in the picture) could be anyone else.

i will support what @Self-Proclaimed King stated.. although it's just a possibility. a great twist tho

What if each tine he met Rena it was a different quintuplet? Just a theory tho

For disambiguation:

<=> SPOILER AHEAD <=>

> [Rena] refers to the present-day, disguised quint who met him at the lake (see "Chapter 42"). There is no "original" Rena, and the proper term to use would be [Young Nakano]. It's revealed that Rena is Itsuki.

> [Rena Nakano] refers to the quintuplets' mother.

> [Young Nakano], [Lolikano], or even [OG Rena] refers to the original Lolikano who: (1) first met Fuutarou in Kyoto (see "Chapter 34"); (2) presumably bought charms with Fuutarou (see "Chapter 34"); (3) took a picture with Fuutarou (?). [Lolikano] can be considered [The Girl in the Picture].