Here are translations I got from elsewhere, first concerning the front:
the caption under the picture says:
“Painted by Ono Saseo.
The natives heartily welcomed the Imperial army.
A balloon saying ‘[long] live great Asia’ was floating in the sky. In the infinitely vast sky.”
At the bottom right of the picture is “2602” for the 2,602nd year of the Imperial reigns (=1942) with Saseo’s signature below.
Then on the other side:
The orange printing at the bottom (in my edit of your original pic) says: “Published by Osamu Shuudan (Osamu Army Group, which is a nickname for the 16th Army) Headquarters.”
At the top right it says "Yubin Hagaki" (Postcard)
At the top left it says: “Gunji Yubin” (Military Mail) and underneath that: “Censored”. The empty box would have to be stamped in red with a censor’s mark to confirm that any sensitive military information had been removed before the postcard could be sent."
And the reverse ,, Not sure of accuracy but it seems about what one would expect from a postcard coming from a hot war zone:
廣嶋市古田町 田方
Den-kata, Furuta Town, Hiroshima City
増田春代様
Haruyo Masuda-sama
拝啓
Dear Haruyo,
其の後永らく御無音に行過ぎ悪しかろ。お許し下さい。
It's too bad to going silent for a long time. Please forgive me.
次に御一家には皆様お変りは有りませんか等お伺ひ申し上げます。
Next, I would like to ask if all of the family keeping well.
亦留守中は色々とお世話様に相成り厚くお礼申上げます。
During my absence, I would like to thank you for your kind cooperation.
降〇〇小生はお陰様で先〇旺盛にて日夜業務に御精働致し〇ります故他〇〇に〇御安心下さい。
I'm in good health and I 've been working hard for the day and night, so please rest assured.
今頃は内地は一番暑中〇〇と思ひます。
I think japan is in the most hot season.
当地は常に南国の夏とは云〇ども今の時節が一番良ひので有ります。
It's always said the land of everlasting summer over here, but the current season is the best.
内地の春秋の時節〇〇〇〇〇す。
I wrote to you when japan is spring/autum.
小〇便にて 敬具
Best regards.
Here are some pics, sorry if they are sideways
imgur.com/a/3Nfj7CxThe beached marus in upper left of first set are confirmed Guadalcanal wrecks, Kumagawa Maru and Yamatsuki Maru - The ruins of the Kumagawa in that 1942 pic are still visible today [clip is 5 years old]
7:13 ,,, So it seems nearly certain the pics and postcard are from Guadalcanal.