This is felt tipped or other porous-tipped pens and markers.
Making the most of Gundam Markers! - HOT TIP
MG PHENEX HOLOGRAM BLUE + WHITE WATER DECAL – The Gundam Place Store
Mr. Hobby Gundam Marker – Lil Thingamajigs Hive
GM100 Gundam Marker Plated Silver, which has been discontinued despite being very popular, will be renewed as part of the Gundam Marker EX series.
Mr. Hobby Gundam Marker EX XGM100 Plated Silver
3pcs/set Mr.Hobby XGMS100 Electroplated Marker Set Gundam Marker EX Series XGM07-White Gold/XGM08-Yellow Gold/XGM100-Silver - AliExpress
MR.HOBBY Marking Pen Model Coloring Oil Gunpla Gundam Plastic GM Line Marker Touchup DIY For Model Production - AliExpress
Gundam Gm08 Yellow Marker
3pcs/set Mr.Hobby XGMS100 Electroplated Marker Set Gundam Marker EX Series XGM07-White Gold/XGM08-Yellow Gold/XGM100-Silver - AliExpress
This marker can easily express dirt and blurred paint with a realistic touch. A water-based wipe-off type is used for safety. Equipped with two types of nibs, fine and thick. GM400 is a pen for blurring already painted GM401-410. Use it to blur the boundary surface. If the nib gets dirty, clean it with a tissue. If it becomes difficult to remove the dirt, use a new blurring pen.
Gundam Marker: GM405 Real Touch Marker Orange 1 (Renewal)