
any update on this manga?

Extras are one complicated thing. Many are simply fan-service and to provide some relief and fun, but taking their content for canon might screw up the characters and their development.
So unless there is a direct, death-proof connection to the plot at some point, extras should better be regarded as non-canon.
For example „Temoral Paradise“ has such a connection. Sensei tied it in fixed into the story. The „Hot Spring Threesome“ on the other hand was designed by sensei with several points of evidence to be non-canon.
So no direct connection to the plot = non-canon, as we don’t know how to place it with the characters.
With this specific one the question would be when to place it in the plot.
This one can only have happened in a tiny short moment of bliss between the moment Akihito „was moved in with“ Asami. Looking back at that time I don’t think they really had that sort of happy, unbothered time back then, between the looming threat of Chernobog, Sudou‘s betrayal, Akihito‘s doubts, investigations and handing out bj‘s to Sakazaki.
So it could happen at some point in the future but hasn’t yet (just like the Pudding extra). If it has not yet happened in the story it’s non-canin for the characters and their development. It could become canon at some point though.

I mean we don’t see every single day of their fictional lives. What do they do on weekends and offdays? And logically speaking, over this course of 20 years of finder going on I assume at least 1 or 2 years must have passed in the manga time therefore birthdays must have came and went. How did they spend it then? Or is everyday just 24/7 gunfights, 365 days a year and no downtime whatsoever.
I mean it’s up to you if you consider it as non canon, that’s fine to me. It’s just that you said it so factually I thought sensei had actually said something like extras are all not canon or something which made me curious. There are many extras that are already proven canon so the rest that can’t be proven either way is up to the reader to decide though I’m pretty sure most people take it as canon anyway. It’s just fiction after all, I see no reason to demand cold hard proof on whether some cute moments actually happened or not, especially when a lot of the mainline content can be pretty fanservicey too like the deserted island chapters and the proven canon temporary paradise, so it’s the same to me.

I just feel that from the point of character development sweet extras like this are hard to take for canon.
If there had been many of those sweet moments of affection and lover's quality time, it would not - in my opinion - fit with the Akihito who doubts what Asami feels for him throughout all of Volume 6-11. Even when they leave the island he still is not sure of what Asami truly feels about him and thinks that they are somewhat detached from each other.
Maybe this is just a personal taste, but a person who spent a large amount of lovey-dovey-dates and cuddle-time would not feel like he has to proof to his lover that he can get information on his own (by blowjobing someone else), nor would he constantly think that the other might loose interest or might be somewhat out of reach.
(⊙…⊙ )

To me the extras have some sweet moments but it’s not super lovey dovey either. Like in the Asami birthday extra, at the end he was still teasing/punishing Akihito and then only said to himself this birthday wasn’t bad but not to Akihito directly. And in Akihito’s birthday Asami kept saying it’s to celebrate children’s day not admitting he wanted to celebrate Aki’s birthday and then only said happy birthday Akihito when Akihito looked to be sleeping. None of them have Asami openly saying Akihito you’re the best I love you or coddling him or anything. Like you said, even when leaving the island Akihito felt some distance and that’s just shortly after Asami outright said there isn’t a day where he didn’t think about Akihito and told him not to leave his side, which is already super extremely clear what he meant. Like even then, Aki is still insecure. And that’s on top of all the many things that happened before that clearly communicated how important he is to Asami. So it’s not outlandish that even after the extras, he would still be insecure. It’s just what sensei loves so much to write. This push and pull up and down and lack of communication that’s been going on for years and will probably do so until the end of the series.
only pervert will like this manga harem -_-