Is there any purpose to the friendships?

[Darkeonz]

Like do they raise the chance of boons rarity, or whatever? I haven't figured out if there's any benefit at all to progressing the friendships?

[dustin1280]

Storyline, and potentially in later versions of this game you might get something mechanically useful.

[Knavenformed]

You get a keepsake from each character the first time you increase the rapport

Only case I think it might have mechanical value later on is Nemesis who has so many different ways to appear on a run, sometimes she just gives you a bonus without any catch and maybe those are tied to higher relationships

[Neo NiGHTS ®]

Not to forget that it's very likely that there will be an achievement (Fate's List) for completing the relationships with everyone.

[Falco]

I hope maxing relationship with the gods gives a small bonus to boon rarity in the future!

[guts' theme (Cut & Looped)]

You unlock bounties/prophecies in the Fated List for certain characters to earn a good amount of rewards.

[Specific Beef]

Originally posted by Knavenformed:

You get a keepsake from each character the first time you increase the rapport

Only case I think it might have mechanical value later on is Nemesis who has so many different ways to appear on a run, sometimes she just gives you a bonus without any catch and maybe those are tied to higher relationships

I think that's just random. I hadn't built my relationship with her past the first step until quite recently, but I was still getting the full range of in-run events with her.

[lborl]

The keepsakes seem to have four stars of upgrade potential even though the standard maxes out at three - saw this by taking one of the Circe rewards that boosts keepsakes by one level "if possible". Presumably maxing each relationship will provide that additional star,

[三Akiyama]

It'll be needed for story purposes like in the first game, I guess.

[Nokturnal]

Currently, first gift you give unlocks their Keepsake. 2nd gift unlocks any Boongivers Fated List entry to get all their boons for a reward and that's about it I think.

Eventually, they'll have story purposes and I assume unlock Companions (Legendary Keepsakes) or something similar like in the first game.