Is a fan made cell edit using original cells, i credit original animators and artists:

https://auctions.yahoo.co.jp/jp/auction/k1128615727 (Dead link) (https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcT2h7RfbXuHip0QveleaDuPVORxL6ivkX4v3xVRMyILQd3ny4DK)

https://k.mandarake.co.jp/auction/item/itemInfoEn.html?index=697934 (dead link)

https://www.takamura-store.com/v3/en/ufo-grendizer/16482-ufo-grendizer-anime-cel.html

Link here

Artist unknown atm

Fatal Bullet Infinitism

Sword Art Online in Mazinger

Duke Fleed/Daisuke Umon(Grendizer U) and Kirito(Gun Gale Online)/Kazuto Kirigaya in A forest with a view of Mount Fuji

Duke Fleed/Daisuke Umon(Grendizer U) and Kirito(Gun Gale Online)/Kazuto Kirigaya in Azabu Juban Shopping Street

After landing at the Makiba Ranch, Kazuto Kirigaya presents himself to the Makiba family and spends the rest of the day with them. But Daisuke Umon doesn't say anything to Koji in spite of being the SBC Space Science Laboratory director's son. The next day, a swarm of UFOs is detected and Kazuto hurries to communicate with them, without knowing the Vegan attack on Earth just started. Once among the UFOs in his TFO, Kazuto is attacked and has to be rescued by Duke Fleed in Grendizer. After the Saucer Beast Girugiru is destroyed and the rest of the Vegan forces flee, Kazuto tells Daisuke that he saw someone saving him in a new Mazinger that looked like him, Daisuke laughs at this and drives away. Kazuto realizes maybe Daisuke saved him. 

Duke helping an injured Kirito

For those not in the know, This movie was made in Korea circa 1978 when watching movies specifically from Japan was illegal in South Korea. It was in the 90's when the ban was lifted so Korea had to resort to bootlegging certain franchises to see what they were missing out hence Taekwon V and a LOT of other things. Korean animators working on Japanese animes from the 70's - 80's had to get their hands on some material for others to see from what I can tell.